iOS Game starts to stutter over time

Hi,

I am currently working on a small iOS game. It is a platformer 2D, where the screen moves at constant speed and the player needs to avoid obstacles that are generated randomly. When I make a clean build of the game, it runs very smoothly. But overnight, when leaving the app in the background it suddenly start to stutter.

The game consists of two scenes: The main menu, and the scene where you play the game. I am using Application.UnloadUnusedAssets and System.GC.Collect before I load the scenes. If I leave the app and re-enter it the stutter remains. It seems like it is a memory issue, but shouldn't the memory get freed in between the two scenes? Also I am using some PlayerPrefs to save my character progression, but if I use PlayerPrefs.DeleteAll the game continues to stutter.

I have looked at this problem for a very long time and I can't seem to find any solution. I can give more details if needed. At this point any guidance will be appreciated.