Weird trail glitch

I have this weird glitch, where on iPhone, if i fire many projectiles at high speed (3000 projectiles to be exact) they leave a ghost trail behind them. Trail that is visible on the screen, even after app goes in background. And it goes away after a few seconds.

In screenshots the trail is not visible at all or i would have posted some.

The projectiles are simple 2D objects with Circle Collider 2D, Rigidbody 2D and a sprite renderer. I'm not using any trail renderers and the camera clear flags is set to Skybox.

What could cause this?

 

I think it just lagged so much, as you used so much physics based object, and it left trails behind

 

I destroy the objects after they reach an edge, so i don't think there's more than 100 objects on screen at one time