Overall after several days of use I can say that version 1.2 is VERY unstable. On my machine it restarts itself seemingly randomly several times a day and sometimes I need to restart Explorer when taskbar and Start menu become corrupted. In no way this release is "release" quality, guys, more like still beta, or even alpha, I dunno
Are you able to put your screenshots / videos on some more internationally recognised websites? Youtube or dropbox or onedrive etc. Unfortunately we are unable to view files on those two sites you have used.
It sounds like you are experiencing some sort of resource leak causing problems. If you are experiencing crashes then any information from the event log would be useful. I suspect a conflict between something else running on the PC and Start11 as this report seems isolated.
If you open taskmanager you should be able to view USER and GDI user handles on the details tab for processes. I would be very interested to know if the handles for explorer.exe are very high.
Do you have any applications which might change their taskbar button icon regularly?
Does it work better if you disable the taskbar enhancement feature?
Edit : We have located a small resource leak which can occur if you open up an application that uses an old non alpha channel icon. This would happen once per icon change, but if the app changes icon OR you open and close windows with this icon over and over the leak would add up. I suspect this may be what you are seeing, but the gdi handle count for explorer would be helpful especially over time and in particular when the issue happens.