Same issue here:
1. Windows 11, 21H2 22000.556
2. Start 11, version 1.16 (beta)
4 monitors, Primary is 3440x1440, 2 are 1920x1080 and 3rd is 4k.
Icons are ungroupped on all monitors ok, but like above two people, the bar on some monitors becomes unresponsive sometimes.
On one other monitor the taskbar works but on the other 3 it's not accessible. I hover over the nonworking taskbars and the hover doesn't show as working. Clicking various items eventually gets the other monitors taskbars to be responsive. Other times it just becomes unresponsive for a bit.
Can still get to the windows via alt+tab, etc. So not too bad.