iOS 8.4 freeze - possibly related to EXC_RESOURCE, WAKEUPS, thread log problem - where to look next?

We are having problems with a freeze-bug that seems to have only manifested after we’ve upgraded our devices to iOS 8.4. Our project was using Unity 4.6.7f1, so we thought upgrading to Unity 5.1.2f1 would solve the issue; however this does not appear to be the case.

According to this thread, several people are encountering a “hiccup” or stutter when iOS generates an error log for a “too many thread wakeups” problem (“EXC_RESOURCE, WAKEUPS, (Limit 150/sec) Observed 269/sec over 300 secs” type error log). We, too, are getting these stutters - however we are also encountering a freeze which may or may not be related.

We have so far found no way of getting any useful information about the freeze - no logs are generated at the time it happens, and the console output remains normal. The game seems to freeze (none-responsive to input, animations stop, screen displays single, non-moving image, etc), but music continues as normal, with both the Xcode and Unity profilers continuing to report as if nothing has gone wrong.

What can I do to pin down the cause of this problem?

I’m listening her, as I get this “EXC_RESOURCE, WAKEUPS, (Limit 150/sec) Observed 269/sec over 300 secs” on our game on all iPhone 4s we have tried on. Both on iOS 8 and iOS 9.

I’m testing on iPhone 4s and iPad 2, as that where the it happens, on all other it works fine.

Rebooting the ipad 2 makes the game work, for sometime. Rebooting iPhone 4s, doesn’t work, game still closes while loading the “Level scene”.