Hola Robert, ¿cómo estás?, I'm from Colombia and I hope your okay, first of all happy new Solar Cycle.
I had exactly the same issue with my guitar controller for Playstation 3, and I say I had becase fortunately I could fix it yesterday.
It's really annoying to play with that kind of trouble and I just did the following and it was completely fixed, after looking for a lot the issue, I first thought it was caused for the red fret button and it wasn't. I've attached a picture where I mark with red circles the place where surely you have the problem. What I did here was to check the connection between the cables and the PCB (the board) and effectively the cable of the red fret hadn't a good connection with the board so I cut the first 5 or 8 milimeters of the cable and soldered again.
As I told you before, I had exactly the same trouble as you and I could fix it in this way, I'm sure your issue is the same, so try this solution and tell me.