If I boot the LIVE media & don't change the screen preferences->LXQTsettings->MonitorSettings to something different, the issues do NOT arise (usually, I was trying to test this here as you'll see in QA-TEST comments, but the portrait-display settings instead of default landscape made me feel a little 'queezy' & I gave up that testing & just changed monitor-settings to reflect my screen setup.
please note: I've got a number of OPEN bugs relating to windows that MOVE/WARP around the screen when I do things... For example
https:/ /bugs.launchpad .net/ubuntu/ +source/ pcmanfm- qt/+bug/ 1804329
"lubuntu 19.04 daily - pcmanfm-qt (dolphin..) moves window position on opening device, folders or adjust size of windows (when on 2nd display only with vertical placement)"
If I boot the LIVE media & don't change the screen preferences- >LXQTsettings- >MonitorSetting s to something different, the issues do NOT arise (usually, I was trying to test this here as you'll see in QA-TEST comments, but the portrait-display settings instead of default landscape made me feel a little 'queezy' & I gave up that testing & just changed monitor-settings to reflect my screen setup.