I have an issue with a Xiaomi Mi 4c: The device boots normally, lock screen appears, I can swipe to enter pin but then it turns black instantly again. I have to hit the power button twice to get back into lock screen. Swiping left to access camera also turns the screen black immediatly. Sometimes when I try to unlock I see the unlocked homescreen (or parts of it) for a split second before it goes dark. When in lock screen, I can access the quick settings from notification bar normally. It seems like it does unlock when I type in my passphrase but turns off the display as well as the home and back buttons on the bottom (they usually respond with vibration when touched, but dont once it goes black). When I try calling while in sleep mode, it rings but doesn't wake up the screen so i can't receive the call. When calling while in lock screeen, it rings and goes black instantly.
I got my Mi4c last November. It still runs on the rom it came with which is some sort of global rom with locked bootloader, google services and english language pre installed as well as some basic apps which cannot be uninstalled. I'm not sure what version it is and since I can't access my phone I don't know how to find out. Also, USB-debugging is not enabled appearently.
The issue first appeared a couple of hours after I had dropped the phone from about half a meter hight which, however, didn't show any immediate consequences.
I did some googeling on the issue with no real results. It would be much appreciated if somebody here had an idea.