iOS lag(slow-mo)

So I have recently builded a game on my iPhone X. On the android(any smartphone) and editor all works fine, game and menu animations are very smooth. But on my iPhone (it happens ± 1 in 10 lvls) game runs like in slow mo(game is twice slower) and UI animations are laggy. It often happens when I hide my game or after ads session.The interesting thing is when I record screen(using iPhone default screen recorder in iOS 11) this "slow-mo" stops, it also stops after restarting lvl(but sometimes it doesn't ) and when I pull down iPhone "curtain". Also it needed to be said that my game is 2D and don't have any advanced graphics . I have set a targetFrameRate to 60 and turned Vsync off, also In quality setting chose a "Fast ", but it didn't help.,So I have recently builded a game on my iPhone X. On the android(any smartphone) and editor all works fine, game and menu animations are very smooth. But on my 1 in 10 lvls game runs like in slow mo(game is twice slower) and UI animations are laggy.It often happens when I hide my game or after ads session.The interesting thing is when I record screen(using iPhone default screen recorder in iOS 11) this "slow-mo" stops, it also stops after restarting lvl(but sometimes it doesn't ) and when I pull down iPhone "curtain". Also it needed to be said that my game is 2D and don't have any advanced graphics . I have set a targetFrameRate to 60 and turned Vsync off, also In quality setting chose a "Fast ", but it didn't help.