Same problem here on my '96 Dak about a month ago. Of course, driving into the sun, bugs splattered all over the windshield, and I had just hit the squirters to clean it all off.
Pulled over into a gas station and left the wiper switch turned on. Peered down into the grillwork in front of the windshield and watched the motor's arm spinning around, without the linkage, which was laying down in the well. The bushing on the motor's arm that snaps into the linkage had disintegrated.
Got a new bushing from the dealer.