I recently upgraded to Workstation Player 16.1.2 and have found the multi monitor functionality to be unstable after Windows is locked for a period of time. When using 2 of my 3 monitors after unlocking (although the symptoms don't seem to occur with locking for only a few minutes) the second monitor appears to be inactive and the mouse pointer tracking doesn't work. The monitor configuration drop down shows single monitor as being selected, and shows the multi monitor configurations, but selecting one doesn't work. Suspending the VM and restarting it solves the issue.
2020 16" MacBook Pro running Win 10 with Bootcamp and a Win 10 guest.