Ios stutters every 30 seconds

Some actors in my game are using an infinite linear animation and after launching the game on ios, I noticed strange stutters every 30 seconds. First of all I blamed my blueprint logic, so I created an empty level with no logic but frame rate display event. And I still lose about 4-5 frames per second. Android is fine. So is that an Engine issue or what can possibly cause those stutters?

P.S The strangest thing is that it happens every 30 seconds, not some random drops.