I had the issue with the selector switch just a bit after the warranty on the JTV-69 ended. The pickups were fine, but the model selection side was very erratic.
I ordered a new switch assembly from Full Compass but in the meantime programmed the POD 500 to select the models I needed for various gigs. That worked fine, but I did finally change out the switch.
There is a plug on one end of a cable on the new circuit board and that plugs into the main board.
For the actual pickups you have to desolder the wires from the pickups and then solder them onto the replacement board. I was able to position things such that I could transfer one wire at a time, so keeping them in order wasn't a big issue. You should always take pictures before starting, and also note the orientation of the old switch.
First off be sure the guitar is disconnected from the POD, if used, and also remove the battery.
Be sure to protect the guitar to avoid damage from dropping solder on the finish, or inside the body.
Discharge any static electricity by at least touching a ground point, or better yet using a grounding wrist strap if you have access to one. This is a good idea if you are in a dry environment where static is an issue. I did my switch change when it was fairly humid so no issues with static.
Note I had tried the non-residue contact cleaner but that really didn't help much. The design of the switch is pretty poor and what appears to happen is that it loses tension over time. It doesn't impact the analog (guitar pickup) side of the switch, but because of the "pulse counting" for the digital model selection there is too much contact bounce and that is what seems to cause the issue.
I plan on seeing if I can engineer a more reliable solution using the old switch and a couple of ideas I have as I expect that the new switch will eventually fail as well.
If you, or your tech, are comfortable with a soldering iron (e.g. you have changed out pickups, selector switches, etc. on your other guitars), then you shouldn't be afraid of doing this repair.