Strange behaviour on iOS - app freezing

My iOS app locks up after a few actions (iOS native navigation/table view). I wanted to see what was happening so I put some debug statements in my timer loop that processes incoming audio. Strangely, when I am constantly generating debug output from my timer the app keeps running fine... but if I take them out, it locks up again.. very strange... almost like some strange quantum observer trick. 


Testing again, I'm now getting the freeze happening even with the debug logs... happens around 64 ticks of the timer after some iOS navigation away and back to the UIView containing my JUCE component.

Its a bug in my code. Today I learnt about the pause button in the Xcode debugger. Very handy to see where your code is getting stuck.