Speaker going off sometimes topic

Hey, i'm having a problem with my moto e ( stock rom ), the volume suddenly goes off until i reboot it in safe mode and then in normal mode ! does anyone have a solution for this please ?
It happened thrice...
Once I did the rebooting thing which is mentioned above...
Second time I just tried putting and removing earphones in earphone slot...
But this time none of it is working... I searched on other websites, the solution was to format the phone or to clear the cache... ?
Can anybody suggest me a better solution cause I don't wanna give my phone to service center peoples...

[Q] Sometimes shut down wnen take a foto with flash? topic

Hello,
First - sorry for my bad English!
These days I bought used ONE m7.Previous owner told me that the phone was not used for more than a month. Now sometimes, only sometimes, when take a shot with flash the phone shut down. After power ON the battery is with more than 10% lower than before this. Hard reset not solved the problem. Is there a hard- or soft- problem?