I'm a "stuff happens" sort of guy, and so before you or anyone else actually working on the guitar, I'd take bunches of photos of the wiring harness/underside of the pickguard. Begin with a couple/few shots of the entire harness for overall reference/orientation, then shots of each potentiometer and the switch. You have to take a few photos of each component, as something will get in the way of something else.
It's a simple and safe task to remove the pickguard screws and simply flip the pickguard over. The wires connected to the pickups should be long enough to do this. The pickguard assembly may have to be flipped onto the strings/pickup areas of the guitar. Put a small towel or something down to prevent inadvertent scratches. I would begin by identifying all the potentiometers (pots); be aware that they will be "flipped" over; be sure that a volume pot is a volume pot. A small piece of paper/tape label will help you identify the specific pot in your photos (e.g., volume, neck; tone, bridge; etc.) Try to read any identification printed on the components. Solder connections may obscure the printing on the pots; read whatever you can. Capacitors (small tube-like things connected at one end to the tone pots) have printing on them (e.g., their capacitance value); don't worry if you don't understand anything -- record the data as you see it. A sketch of all this (expanded) can also be helpful; not easy to do without it looking like a plate of spaghetti and meatballs. This is sort of a PITA, but it is good to have the info.
Yeah, there are a lot of techs out there who might say they can help you out, which very well might include changing your wiring without your permission as a well-meaning but erroneous interpretation of what you should have. I would not go to a guitar tech, unless you could find one that has vast experience with Ricks. Rather, I'd find a reputable electronics repair shop (though this may be difficult in age of disposable electronics). The basic components of the wiring harness are basic -- been around for decades, so anyone reasonably competent can look at your wiring and diagnose your problem(s). So, seek someone out, agree that the initial inspection of the wiring is for diagnosis only, and that you will return to talk about the specific repairs required. Proceed only if both of you agree.
Perhaps a part should be replaced. Sometimes a solder joint of two goes "cold" and simply needs to be "re-soldered" to improve the respective connection.
If you are anywhere near this place, it might be your best bet for repair advice, and perhaps the repairs themselves:
https://www.rickysounds.co.uk/Well, check it out. I would get any required parts from them.
That's all I have. (You can't be too careful.) Good luck.
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