dell [optiplex] 780 (c2q-q9400, 8gb, amd/ati cedar radeon hd 5000/6000/7350/8350)
Xubuntu 19.10 daily ISO QA-Test - occurred again.

Theo's (previous) requested command (which fixed the issue on running it)

xubuntu@xubuntu:~$ XFSETTINGSD_DEBUG=1 xfsettingsd --replace --no-daemon

(xfsettingsd:4359): xfsettingsd-WARNING **: 12:42:38.323: Property "/Gdk/WindowScalingFactor" has an unsupported type "guint".
xfce4-settings(xsettings): _XSETTINGS_S0 registered on screen 0
xfce4-settings(xsettings): 31 settings changed (serial=0, len=1256)
xfce4-settings(xsettings): resource manager (xft) changed (len=1330)
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): CRTC 79 assigned to HDMI-0.
xfce4-settings(displays): CRTC 79, output list[0] -> 83.
xfce4-settings(displays): CRTC 80 assigned to DVI-0.
xfce4-settings(displays): CRTC 80, output list[0] -> 84.
xfce4-settings(displays): Total 2 active output(s).
xfce4-settings(displays): Normalized CRTC 79: size=1280x1024, pos=0x0.
xfce4-settings(displays): Normalized CRTC 80: size=1024x1280, pos=1280x8.
xfce4-settings(displays): CRTC 80 must be temporarily disabled.
xfce4-settings(displays): Disabling CRTC 80.
xfce4-settings(displays): min_h = 200, min_w = 320, max_h = 8192, max_w = 8192, prev_h = 1024, prev_w = 2560, prev_hmm = 270, prev_wmm = 677, h = 1288, w = 2304, hmm = 341, wmm = 610.
xfce4-settings(displays): Applying desktop dimensions: 2304x1288 (px), 610x341 (mm).
xfce4-settings(displays): Configuring CRTC 79.
xfce4-settings(displays): Applying changes to CRTC 79.
xfce4-settings(displays): Applying CRTC 79 Transform: x=1.000000 y=1.000000, filter=nearest.
xfce4-settings(displays): Configuring CRTC 80.
xfce4-settings(displays): Applying changes to CRTC 80.
xfce4-settings(displays): Applying CRTC 80 Transform: x=1.000000 y=1.000000, filter=nearest.
xfce4-settings(displays): Configuring CRTC 81.
xfce4-settings(displays): Configuring CRTC 82.
xfce4-settings(pointers): initialized xi 2.3
xfce4-settings(keyboards): initialized xkb 1.0
xfce4-settings(keyboards): set auto repeat on
xfce4-settings(keyboards): set key repeat (delay=500, rate=50)
xfce4-settings(keyboards): don't set numlock
xfce4-settings(accessibility): AccessXKeys disabled
xfce4-settings(accessibility): stickykeys disabled
xfce4-settings(accessibility): slowkeys disabled
xfce4-settings(accessibility): bouncekeys disabled
xfce4-settings(accessibility): mousekeys disabled
xfce4-settings(keyboard-shortcuts): 31 shortcuts loaded
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(fontconfig): monitoring 163 paths
xfce4-settings(workspaces): 1 desktop names set from xfconf
xfce4-settings(displays): CRTC 79 assigned to HDMI-0.
xfce4-settings(displays): CRTC 79, output list[0] -> 83.
xfce4-settings(displays): CRTC 80 assigned to DVI-0.
xfce4-settings(displays): CRTC 80, output list[0] -> 84.
xfce4-settings(displays): Total 2 active output(s).
xfce4-settings(displays): Normalized CRTC 79: size=1280x1024, pos=0x0.
xfce4-settings(displays): Normalized CRTC 80: size=1280x1024, pos=1280x8.
xfce4-settings(displays): CRTC 80 must be temporarily disabled.
xfce4-settings(displays): Disabling CRTC 80.
xfce4-settings(displays): min_h = 200, min_w = 320, max_h = 8192, max_w = 8192, prev_h = 1288, prev_w = 2304, prev_hmm = 341, prev_wmm = 610, h = 1032, w = 2560, hmm = 273, wmm = 677.
xfce4-settings(displays): Applying desktop dimensions: 2560x1032 (px), 677x273 (mm).
xfce4-settings(displays): Configuring CRTC 79.
xfce4-settings(displays): Applying changes to CRTC 79.
xfce4-settings(displays): Applying CRTC 79 Transform: x=1.000000 y=1.000000, filter=nearest.
xfce4-settings(displays): Configuring CRTC 80.
xfce4-settings(displays): Applying changes to CRTC 80.
xfce4-settings(displays): Applying CRTC 80 Transform: x=1.000000 y=1.000000, filter=nearest.
xfce4-settings(displays): Configuring CRTC 81.
xfce4-settings(displays): Configuring CRTC 82.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): CRTC 79 assigned to HDMI-0.
xfce4-settings(displays): CRTC 79, output list[0] -> 83.
xfce4-settings(displays): CRTC 80 assigned to DVI-0.
xfce4-settings(displays): CRTC 80, output list[0] -> 84.
xfce4-settings(displays): Total 2 active output(s).
xfce4-settings(displays): Normalized CRTC 79: size=1280x1024, pos=0x0.
xfce4-settings(displays): Normalized CRTC 80: size=1024x1280, pos=1280x8.
xfce4-settings(displays): CRTC 80 must be temporarily disabled.
xfce4-settings(displays): Disabling CRTC 80.
xfce4-settings(displays): min_h = 200, min_w = 320, max_h = 8192, max_w = 8192, prev_h = 1032, prev_w = 2560, prev_hmm = 273, prev_wmm = 677, h = 1288, w = 2304, hmm = 341, wmm = 610.
xfce4-settings(displays): Applying desktop dimensions: 2304x1288 (px), 610x341 (mm).
xfce4-settings(displays): Configuring CRTC 79.
xfce4-settings(displays): Applying changes to CRTC 79.
xfce4-settings(displays): Applying CRTC 79 Transform: x=1.000000 y=1.000000, filter=nearest.
xfce4-settings(displays): Configuring CRTC 80.
xfce4-settings(displays): Applying changes to CRTC 80.
xfce4-settings(displays): Applying CRTC 80 Transform: x=1.000000 y=1.000000, filter=nearest.
xfce4-settings(displays): Configuring CRTC 81.
xfce4-settings(displays): Configuring CRTC 82.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): CRTC 79 assigned to HDMI-0.
xfce4-settings(displays): CRTC 79, output list[0] -> 83.
xfce4-settings(displays): CRTC 80 assigned to DVI-0.
xfce4-settings(displays): CRTC 80, output list[0] -> 84.
xfce4-settings(displays): Total 2 active output(s).
xfce4-settings(displays): Normalized CRTC 79: size=1280x1024, pos=0x0.
xfce4-settings(displays): Normalized CRTC 80: size=1280x1024, pos=1280x8.
xfce4-settings(displays): CRTC 80 must be temporarily disabled.
xfce4-settings(displays): Disabling CRTC 80.
xfce4-settings(displays): min_h = 200, min_w = 320, max_h = 8192, max_w = 8192, prev_h = 1288, prev_w = 2304, prev_hmm = 341, prev_wmm = 610, h = 1032, w = 2560, hmm = 273, wmm = 677.
xfce4-settings(displays): Applying desktop dimensions: 2560x1032 (px), 677x273 (mm).
xfce4-settings(displays): Configuring CRTC 79.
xfce4-settings(displays): Applying changes to CRTC 79.
xfce4-settings(displays): Applying CRTC 79 Transform: x=1.000000 y=1.000000, filter=nearest.
xfce4-settings(displays): Configuring CRTC 80.
xfce4-settings(displays): Applying changes to CRTC 80.
xfce4-settings(displays): Applying CRTC 80 Transform: x=1.000000 y=1.000000, filter=nearest.
xfce4-settings(displays): Configuring CRTC 81.
xfce4-settings(displays): Configuring CRTC 82.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): CRTC 79 assigned to HDMI-0.
xfce4-settings(displays): CRTC 79, output list[0] -> 83.
xfce4-settings(displays): CRTC 80 assigned to DVI-0.
xfce4-settings(displays): CRTC 80, output list[0] -> 84.
xfce4-settings(displays): Total 2 active output(s).
xfce4-settings(displays): Normalized CRTC 79: size=1024x1280, pos=1280x0.
xfce4-settings(displays): Normalized CRTC 80: size=1280x1024, pos=0x0.
xfce4-settings(displays): CRTC 80 must be temporarily disabled.
xfce4-settings(displays): Disabling CRTC 80.
xfce4-settings(displays): min_h = 200, min_w = 320, max_h = 8192, max_w = 8192, prev_h = 1032, prev_w = 2560, prev_hmm = 273, prev_wmm = 677, h = 1280, w = 2304, hmm = 339, wmm = 610.
xfce4-settings(displays): Applying desktop dimensions: 2304x1280 (px), 610x339 (mm).
xfce4-settings(displays): Configuring CRTC 79.
xfce4-settings(displays): Applying changes to CRTC 79.
xfce4-settings(displays): Applying CRTC 79 Transform: x=1.000000 y=1.000000, filter=nearest.
xfce4-settings(displays): Configuring CRTC 80.
xfce4-settings(displays): Applying changes to CRTC 80.
xfce4-settings(displays): Applying CRTC 80 Transform: x=1.000000 y=1.000000, filter=nearest.
xfce4-settings(displays): Configuring CRTC 81.
xfce4-settings(displays): Configuring CRTC 82.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settdell [optiplex] 780 (c2q-q9400, 8gb, amd/ati cedar radeon hd 5000/6000/7350/8350)ings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.
xfce4-settings(displays): RRScreenChangeNotify event received.
xfce4-settings(displays): Refreshing RandR cache.
xfce4-settings(displays): Detected CRTC 79.
xfce4-settings(displays): Detected CRTC 80.
xfce4-settings(displays): Detected CRTC 81.
xfce4-settings(displays): Detected CRTC 82.
xfce4-settings(displays): Detected output 83 HDMI-0.
xfce4-settings(displays): Detected output 84 DVI-0.
xfce4-settings(displays): Noutput: before = 2, after = 2.