To Reproduce:

1. Build and deploy the project attached to the comment to an iPhone 6S.
2. Press the home button and reopen the app (might be necessary to repeat this several times (up to 5-10)).

The app crashes in PresentGles / [surface->context presentRenderbuffer:GL_RENDERBUFFER];
https://gist.github.com/qwyt/1cfea253b6eb839f8b9c (stacktrace)

The scene which is loaded only has a mesh with a standard shader and a script which continuously switches between it and another scene with a canvas and an UI image.

Could only reproduce on an iPhone 6s, so this might be A9 specific, couldn't reproduce on:

iPhone 6+ iOS 9.0
iPhone 6+ iOS 8.0
iPad mini 4 iOS 9.0
iPad mini 2 iOS 9.0

Only reproducible with GLES2, no crash when using Metal

UPDATE:------

Seems to be an A9 driver issues, we've submitted a bug to apple:

Radar: 23225771 Crash in EAGL presentRenderBuffer when awaking from backgrounded state

and we're waiting for their response.

UPDATE:------

Apple have fixed this bug in the upcoming iOS 9.3.3.

The bug in the current iOS is related to accessing mips in cubemap textures, so work arounds for supporting devices before this update include not using cubemaps and using legacy cubemap assets (which allow mipmaps to be turned off).

Unfortunately, even with the fix in the new iOS, it is still possible to get crashes on A9/A9x devices when using openGLES. These cases seem to be related to reflection probes and can be avoided by marking reflection probe textures as uncompressed. We are continuing to investigate and talk to Apple about these remaining crashes.