LOL, my numerous Feedback to Apple goes to Cloud Neverland.
Since downgrading to iOS 8.4 is forbidden and impossible unless someone figures out a hack (one day some bright hacker will), we are stuck with annoying new bugs with each update.
The best thing to do when you update and the Game Center bug is finally squashed, don't bother updating the iOS anymore. Your apps will still work for quite some time. You most definitely will get continuous Apple nag notifications to update, but try to resist lol.
I bought my iPhone and iPad outright and it wasn't cheap and I want it to "JUST WORK" like Apple used to claim. I expect better iOS testing by Apple software engineers before being release to the general public. It's quite disheartening to constantly be searching for fixes for new bugs introduced. We are unable to access iOS file system so there is only so much we can do.