I've been using my A5 for more than four years now (bought it in February 2016). All has been fine until today when the authentication methods (fingerprint and the 4-digit PIN) suddenly stop working. Yesterday, the problem went away when I restarted the phone. But today, the authentication methods work only after I restart the phone, and when the phone is locked after one minute of no activity, I can't get back in. I have already tried the Safe Mode and the authentication methods work as normal there. FYI, the OS is Android 7.0 (Nougat).