Why is my audio randomly cutting out?

I have my linux mint pc hooked up to my LG TV 55LN5758-ZE via HDMI. The TV is hooked up to a speaker setup using the H/P OUT connector. A while ago, maybe half a year or so, the audio started to just not work after waking up from standby or turning off the pc. This was mostly fixed by just rebooting, sometimes i needed to reboot twice though. Now after some time audio started to cut out just whenever. at first i could just change the volume using the volume keys of my keyboard and it would work again after changing it a little. then it took longer and longer and i had to ramp up the volume to max, then min, then max again a couple of times to get it working again. Now it is at a point where it almost never works using the keyboardd. Instead i have to turn the tv audio up and down until it works again (mostly after going up to max volume once and when going down at about 60% it cuts back in).
I assume there is probably some error with the soundboard of the tv. The hdmi cable seems fine. I just dont understand why it changes from being fixable with changing the volume a little, requireing huge changes or a restart and finally just responding to a volume change on the tv. any ideas?