1955 buick special electric wiper motor conversion
 

I converted to electric wipers a few years ago and everything was going well. until today wipers are not moving in a full range of motion. the rest in the middle of the windshield and move a total range of 2 inches up and 2 inches down. any help?
https://tinyurl.com/4a36xpa3

above is youtube link to my problem.
below is the link to the product i purchased

https://oldbuickparts.com/product/wiper-motor-electric-12v-4/