Is there anything other than a failure of the wiper motor that will cause them not to park?

they just stop when I turn off the switch.

 Thanks in advance for help/ideas!

Most wipers have a contact in the drive mech.  That opens when they are in the park position.   When you switch them off, power continues through that switch until it opens.  

With the brat there’s a six pin plug above the driver’s feet behind the kick panel. This plug should have a corresponding mate that has a single yellow wire that loops back into the plug and into the wiring loom. 

Without this loop, the wipers will never self return. 

Cheers 

Bennie