Frustrating tailgate electrical gremlins....

Had a problem with the brake lights being on all the time EXCEPT when depressing the brake pedal, plus an ongoing issue with a sluggish/temperamental rear wiper. Opened up rear light socket hatches & checked grounds, then opened up tailgate panel to try to figure out wiring.

Got the lower brake lights to work properly, somehow, and -- after unhooking the wiper motor from the control arm and testing -- determined that a new motor was in order. Control arm could do with some lubrication, but I got the new wiper motor hooked up and working better (regular & intermittant) from the switch at steering column. But....

Now the center brake light doesn't work at all. And, if I have the rear wiper on, it stops when I press the brake pedal!

Did I hook up something incorrectly? Seems like the center brake & light rear wiper grounds both pass through a couple of harnesses & wiring bundles inside the tailgate. Any suggestions on how to proceed? A wiring diagram/picture would be helpful...
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'91 940T 153k; '92 745 186k