The Achievements Screen Animations play when tabbing out & back into the game. This only affects the Achievements Screens.
How to reproduce:
Go to the Achievements Screen with Screen Animations turned on
Tab out & back into the game
Observe the Screen Animation playing, when tabbing out & back into the game
Observed Results: The Screen Animation plays after tabbing out & back into the game
Expected Results: The Screen Animation should not play after tabbing out & back into the game
The report you have submitted is working as intended: UI is supposed to work this way. Resolving as "Works As Intended"