Have you done the paperclip test?
I goes something like this:
(for guitar but nevertheless test the magnetism over each pole):
It's nothing you can set the pickup height with since it is different for each string, since they have radius. But it's definitely something you can test if the magnetic field is the same all across and along the pickup and above each pole piece, especially since you have no adjustable pole pieces. You can do this on the bridge RAIL pickup too, provided it is one of the rail types.
I don't know if any mods are made on Ric pickups, but generally speaking of ceramics, is that ceramics does not conduct electricity as opposed to - say - alnico. Ceramic pups usually have a magnetic bottom plate, and some other pickups (with Alnico no less) have some added/modded bottom plates for added clarity or lower thump or higher end or increased output. It can vary greatly the reasons behind those bottom plates. Now, if something beneath the pickup has turned loose or is slightly askewed at one end or the other the magnetic field can be greater on one side than the other, or as in your case, all of a sudden, in the "middle" so to speak. It can also involve some wiring not connecting properly or soldering getting loose.
The one thing I am intrigued about is: Has it ALWAYS been like this, since you've bought it, or has it been like that since you got it back from repair only?
This can be hard to detect, because you may have turned accustomed to it, and just discovered it by now, while earlier, it wasn't any of your concern. There's one thing too you can try, a bit far fetched but it has helped sometimes:
You can change the pickup to the other way around. Not upside down (of course), but that the pole piece that resides unde G-string now, resides under the E-string instead. Easy and cheap and doesn't cost you more than 15-20 minutes extra.
It may have been put back the wrong way after restoration and refretting? Can it just sit in one way? Usually this just affects when two pickups are in use at the same time (ie in pararell or serial mode) but nevertheless it has to do with all that north-south thing, phase reverse and bla bla...