So I took my 89 xj6 to get the windshield replaced and put on new wipers but when they returned the car to me the wipers were not working properly. In high and low speed they aren't able to park and then also in intermittent the glitch, as in they will go 25% of the way stop for a second then finish to the other side then repeat. Any advice?

 

It sounds like they may have taken the wiper arm off (understandable) and not put it back on in the right place. Maybe try taking it off, run the motor a few cycles and the put the arm back on in it's proper park position. Good luck.