HTC One M8 Factory Reset not working My One M8 has started acting very strangely, as if it is unable to write to its local storage any more. Every time I restart it, it's like it gets reset to a previous point in time - files that were on the local storage have gone, Apps that I uninstalled have come back and so on.

I've tried to do a factory reset via the bootloader, which appears to complete successfully, but then when the phone restarts, it's back to the same state it was in before I ran the factory reset!

Any ideas? The phone is stock, locked and unrooted.
The issue appeared to be the built in /sdcard filesystem had become suspect and was being mounted read-only. Rooting the phone could probably have resolved it but it was still under warranty - so I just had it replaced.