I had this same thing happen a number of times. In my case it turned out to be a software glitch that had developed for reasons known only to the system. I rolled back a couple of versions of the software and then did a OTA update to the latest version and the problem was fixed. The glitch has affected both of my H520 systems at different times and the fix was the same.
It might work for you, hope it does.
I tried your recommendation it did not work I think there is no choice and should open the stI had this same thing happen a number of times. In my case it turned out to be a software glitch that had developed for reasons known only to the system. I rolled back a couple of versions of the software and then did a OTA update to the latest version and the problem was fixed. The glitch has affected both of my H520 systems at different times and the fix was the same.
It might work for you, hope it does.