IOS EAGLContext presentRenderBuffer is blocking

I observe that on iOS 8, sometimes my apps get blocked on startup (_semwait_signal) when [_oglContext presentRenderbuffer: GL_RENDERBUFFER] is called and it clears up after a few seconds, especially on older devices like iPhone 4S. Need to know what can cause the presentRenderbuffer to hang? Any ideas. This only happens on iOS 8.