Notifications and ringont mute for no reason

[event3horizon]

I have an htc one m9 stock running android 6.0

I've had this annoying issue since day 1 with this phone. What happens is my ringtone and notifications will just stop sounding out for no reason. When i toggle the volume up button i see the speaker icon crossed out as if i muted it but i never did!! I can manage to unmute it and ringtone will work but sometimes notifications totally stop ringing out unless i reboot the phone. Out rageous! I miss so many calls and texts because of this. I don't know how i can trouble shoot this. Any ideas? Btw dnd mode is off.

 

[wildclip]

Maybe it's a rogue app that's controlling your volume settings?

 

[event3horizon]

Thought about it but i have many apps. I don't recall it happening after a particular one. Once again my notifications are muted. Hell even if i go to the sounds control panel and ring it out manually when i choose the sound it doesnt ring out.