As many of these as I have worked on in the past, I have not encountered a problem like this. I have an 85 with the intermittent wiper control. Everything works, but when I turn the wipers off, the left (Drivers) wiper parks just fine, but the right (pass) wiper lands about 40% of the way up the windshield. I just have to shove it down into place when I shut them off and they just stay there until I use them again. No slop in the wiper arm mechanism/linkage.
I always believe that when a solution is found, a follow up is in order, so.......The follow up:
After not being able to sense any slack or slop in the wiper assembly, the logical move was to remove the wiper motor and take it apart. Sure enough...the contactors were totally burned. I have not quite figured out why having the 'parking" contactors burn would cause un-even wiper arm parking, but sure enough it did in my case! I tested the theory by cleaning the contacts, re-installing and the wipers worked perfectly and parked properly.
I bought a Cardone re-built unit, installed it, and now, no issues!
Thanks to those of you who offered suggestions. I really appreciate all of you!