For the first few months, bluetooth headsets and car bluetooth worked fine with my mi5 Prime (3 GB/64 GB). Then forward, back and pause stopped working, but volume up/down were OK. In Additional Settings/Headphone remote buttons, I've toggled back and forth between 'Control volume level' and 'Control music playback'. The selection makes no difference. (Why is this even a choice? I used to be able to control both using short presses for volume and long ones for playback.) 'Assign buttons' just gives the message 'No headphones detected' (although a bluetooth connection is active). All the other menu options, including 'Choose headphones type' are greyed out, and always have been. I've tried various headsets (Samsung, Sony), two different cars and two music players. No improvement. In fact, the situation seems to be deteriorating. Down-volume control switched to the former on/off button...for a while. Now that button opens the headset mike and there's no way to decrease playback volume (although I can still increase it). Since the phone's bluetooth once worked fine, I thought I would try a factory reset, but that seems to involve reflashing ROM and, after rooting around in this forum for a while, I've come to suspect I have a fake one: MIUI by xiaomi.eu, 188.8.131.52(MAACNDB) Stable. I bought the phone from *******. I tried 'Reboot to recovery mode' in the Updater app, but the screen just went black and then the phone turned off. I guess that means it's locked. What now? You can tell I'm in way over my head.