There is a smartphone with anroid 5.1. Another user installed an app from a non-verified source (some hacks for Clash of Clans afaik). To uninstall it I have to drop its administrator rights in
Settings -> Security -> Device administrators. The problem is that when I click to uncheck it, device locks and I hear two check sounds (check and uncheck, I suppose).
When I go to settings again the checkbox is still checked. The same behaviour when using safe mode.
How to remove malware-originated administrators?