Does the problem persist if you remove unity8-desktop-session-mir?
I thought the problem sounded like XMir but your logs say XMir is not in use: (WW) "xmir" is not to be loaded by default. Skipping.
Also a second question: Can you please run "xrandr" while experiencing the problem and paste the output?
Does the problem persist if you remove unity8- desktop- session- mir?
I thought the problem sounded like XMir but your logs say XMir is not in use:
(WW) "xmir" is not to be loaded by default. Skipping.
Also a second question: Can you please run "xrandr" while experiencing the problem and paste the output?