My girlfriend bought a One M8 about 2 months ago and has had problems with it from about 2 weeks in.
Basically after buying the phone new, after about a week of use, the Earpiece speaker completely stopped producing sound - during calls and in general, for example when playing music, YouTube, etc. To check whether it was a hardware fault, I performed a factory reset which cured the problem.
A few days later the problem reoccurred. This time we took the phone back to the point of purchase, explained all this. I pushed for a full replacement explaining that a factory reset solves the problem but it reoccurs, but obviously the just gave me back the same phone.
Phone worked for about 2 weeks, then same thing. Tried another factory reset this time not restoring in any way (just to try as I know the Notification light not working could be due to this), same thing after a week.
Does anyone have any ideas? This is totally infuriating and I can't make any sense of it. Obviously its not the hardware, but can't understand what is going on hear. If anyone can shed some light it would be much appreciated.