Catalina/MacBook Pro: Screen Flashes When Changing User

UPDATE: I took my MacBook Pro the the Apple store yesterday for a battery replacement and while there I asked if the screen flash/blink was anything to be concerned with and was told it was not. So, I gues we can consider this resolved.

Thanks.

If I select Lock Screen from under the Apple menu item I am only shown the current user on the lock screen and there is no way to select another in order to switch users. If I log out one user under the Apple menu item, then I can choose another user on the lock screen. Then I press the right facing arrow to log in and the screen blinks immediately after that. Just one quick blink. Like I said, I doubt it's anything...

I have not seen anything along the lines of rotating cube such as you describe or anything else.

Ahh... now I see the "cube animation". Clicking on the Switch User icon I see the cube "transition" to use a word that a video editor might use. The existing screen spins out of view before the next screen is drawn. When I do that I see a black screen for a faction of a second after the cube finishes rotating before other user icons are shown. That's not the issue I wrote about in my OP of course, but at least I understand the reference to spinning cube from your post above.