Look into how Control Rotation works. It’s a property of the Player Controller pawns and their cameras can (optionally) inherit from. You could attempt to Set Rotation of a pawn all day long, only to have it reset to control rotation next (or even the same) frame.
Hard to tell what is going on in the animation, and even harder to suggest anything tangible without knowing:
how the involved pawns work
how the controller is set up
how you want it to work
But it seems exactly like the abovementioned scenario.