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Go to your Google App store, and select My Apps, select ALL.. Have a look at your RECENTLY installed apps and try uninstalling them 🙂
I hope that helps, since android only upgrades when an app is trying to modify or update its system files!
And you may or may not be root as well; but that is another story lol
Also check if you have installed any app that clears the cache, if so try to remove that app.