Prestolite wiper park function question

The David Bass rebuilt Prestolite wiper motor in my 67 Ambassador almost never wants to properly "park" the wipers when the switch is turned to off. Usually the wipers will simply stop in place or park half way up. I tried a new wiper switch and it made no difference. The wipers wipe normally as they should. As I'm sure most everyone knows removing the wiper motor to be sent back for fixing is a major pita. I'm assuming the problem is within the gear housing where the wires are connected. The gear case cover looks like it's reasonably easy to remove without the need to remove the entire motor. Does anyone have any experience what what is inside? The TSM shows a parking switch but gives no details or drawings on how it's supposed to be actuated. Maybe mine just has dirty or bad contacts or is somehow broken ? Help would be appreciated !

Ramblinrev, I'm pretty sure that the switch is grounded OK to the dash through it's mounting shaft. It's tightly secured but I'll check it with a ohm meter just to be sure. The wiper's variable speed control function works properly and all the dash lights that illuminate the "lights", "wiper", "ignition", "lighter" and "a/c cooling" bezel lenses along the lower dash are lighting as they should. I'm almost 100% sure the issue is within the motor itself.

The cam moves the rocker at the top which moves the contact arms.
Edit- this was disassembled and re-riveted.



Edited by Steve_P - Jan/20/2021 at 4:11pm

Took the cover off and opened up the housing this morning. I can't see where the pin on the guitar pick shaped rotating cam is supposed to engage
on the driven main gear.