When in full screen with 3D graphics enabled, I get a pulse of the screen dimming/brightening about every second. Turning off 3D Graphics solves the problem, but my intended use uses 3D graphics so that doesn't really help me. The suggestion in a 2012 Knowledge Base article of turning Full Screen Minibar to "always on" also works, but I'd prefer not to have that always there. (And it claims the underlying issue was fixed in 5.0)
On the latest Big Sur beta, and Fusion Player 12.0.0. This is a brand new VM with a brand new installation of Windows 10.