I've also been having this problem on the latest cumulative update and 3.9.16 doesn't seem to fix it fully unfortunately. I have a 2 monitor setup and it usually manifests on either one at random after each reboot where the taskbar will be stuck stuck as a fully transparent one with icons/items/time visible, but still acting like it is hidden so windows can fill the space and get overlaid with the icons/etc. In my case, it seems to more often than not be my non-primary monitor upon reboot/login and I can usually fix it by manually flipping auto-hide on and off again, but sometimes that doesn't work either or it will be on my primary instead and not be fixable with flipping auto-hide, it's very random.
Would love to add any logs/dumps or test possible fixes!
Autohide off (both in Settings -> Taskbar and SAB 'Automatic hiding/shyness' settings off):
Autohide on:
Settings (enhanced classic start menu on):
