Wiper ghosts and reverse lamp plexiglass

My '98 Aurora's wipers have a mind of their own....sometimes they do not turn off all the way, they flutter for a while lifting just a little....any suggestions? Also looking for an inexpensive (new = $120) way to replace the plexiglass that cover that reverse lamp on license plate assembly - any suggestions? Having a heck of a time!

I'm intrested in this,too. The wipers on our 97 have the same problem. The module on the front of the wiper motor was replaced twice under warranty. I've had the the module out and cleaned connectors, touched up the solder joints on the pcb and adjusted the park contacts on the module to no avail. The problem will go away for a while and then resurface. No web site I've been to has an answer for this.

PLEASE......if you figure this out , let me know. My '97 does it..
sometimes they will just lift up and set down for no reason... other times if they have been on, when you turn them off, they "bounce" up and down 5-10 times before they go off/ When we told the dealer, he acted like we were crazy........