Rare speed up when re-opening citra

I recently update to the newest version of Citra, the one with the SDL sound fix… And I notice something, mmm… Interesting maybe?
I was playing Project X Zone with the Xbox controller, and I know that in some movements the FPS drops about 5~10%, but the controller’s battery die, and I have to exit Citra, and when I play again, the FPS barely drops.
I don’t know why, but maybe this could be a future reference for improvement.

My PC specs are just in case:

Intel Core i5 7600
GTX 1050 no-ti
8GB Ram
Win 10