Roland JV-35: No Sound Issue

I am looking at purchasing a JV-35 from a friend. It’s in mint condition with the exception of one problem. Sound output is sketchy. Sometimes, you can barely hear the sound and then at other times, it will briefly work fine. This is from every output port. I would love to have this board, but I am concerned about not being able to diagnose the problem or fixing it.

Does anyone else have experience with this and do you have any advice? From what I can tell, it has some very nice sounds.