Unity AR causes lag on the whole game

Question

I'm developing a game which has several minigames, one of them is a AR game, it works as expected but when I close the AR minigame (load other games scenes) , All games run with lag(like 20 fps or even less) which only happens after loading the AR minigame, before loading AR they run smoothly. Should I disable the AR somehow before changing the scene? Is there a way to avoid the lag? thank you