Comment 22 for bug 711591

[ 5.368826] [drm] nouveau 0000:00:12.0: 5: 0x00000340: type 0x40 idx 5 tag 0xff
[ 5.368833] [drm] nouveau 0000:00:12.0: Parsing VBIOS init table 0 at offset 0xE333
[ 5.368855] [drm] nouveau 0000:00:12.0: ======= misaligned reg 0x001020FB =======
[ 5.368861] [drm] nouveau 0000:00:12.0: ======= misaligned reg 0x001020FB =======
[ 5.368891] [drm] nouveau 0000:00:12.0: Parsing VBIOS init table 1 at offset 0xE484

misaligned reg sounds weird. Other than that (and a lot of other nouveau verbosity) there doesn't seem to be an obvious error message in dmesg, nor anything in /var/log/Xorg.0.log to indicate that the system was in a broken state.

Are you certain you did apport-collect while the system was exhibiting the issue?