iOS Game Centre notification banner repeatedly showing - why?

Hello,

I'm just installing Game Centre features on my game which I've not done before - all seems to be going well apart from the banner that shows notifying the player of the achievement keeps coming on screen, then disappearing, then it comes back, and repeats continuously.

Any ideas?  code attached.

Thanks

Fixed this - the custom event was been called from inside an Always update.

I'm surprised it continued to call it though after the scene had changed?  Unless all the events were queued up and were still  being called one after another even though the scene had changed?