Classica AGC issue

Hi, i’m new here and I work in Serbia in the hearing aid service. I have an issue with a phonak classica agc. I have tried changing the mic and rec, as well as the pot and mto switch. the result is always the same, the device works only sometimes. I left it with a battery and left it for half an hour and when I came back it was working. i tried touching all the parts to see when it would turn off but it didn’t. I put it down and after a minute it turned off again. Does anyone have an idea what it could be? Just out of curiosity…Thanks