Your post brings back memories, none of them very fond.

With any wiper gremlin the place to start seems to be clean the ground on the motor. That is located on the bottom side of the wiper motor, and be prepared for green when you see the ground. There are three nuts on that hold the wiper motor to the firewall, and be careful and lift the motor away from the firewall to clean it. That has cleared up issues for several folks reading their posts.

Before you start this you want to get a new dough nut seal, that what seals the motor shaft as it passes through the firewall. That is a dealer part and you want a new one unless yours has recently been changed out. If you have not ever pulled a wiper motor, you need to take all the screws out of the glove box and pull it out. Then way up at the very top there is a slide on clip that holds the wipers arm to the motor, pop that off (I use a long set of needle nosed pliers). Then before you can remove the motor, you have to take the arm off the motor you can not get the motor loose without removing that arm. There is an 8 or 10 mm nut holding that to the end of the motor I use a 1/4 drive socket and reach up in there. I can take the clip off and remove the nut by feel now, but practice makes perfect.

If cleaning the ground fails to solve your problem and chances are it may not (still worth trying), I would suspect the motor. Lots of posts in the past about checking the wiring in the stalk and relays. I went through extended wiper heck over a two year period and learned way more about them than wanted to.

Changed the connector going to the motor, mine was a corroded mess. Added a ground wire from the firewall ground strap to the motor frame, and that did actually solve one gremlin in the intermittent circuit. Went the PUP route pulling motors (to the tune of four or five) but it seemed every donor part had an issue like stopping in the middle or top, no intermittent (full speed and dead stop), no high speed, no low speed, and my personal favorite blowing the fuse in a deluge on the way home in the dark.

Tried the BB magnet glue thing and made a mess out of one. Had to put a donor one with an other issue in to drive the car. Chased my tail with relays, stalk wiring, and looking for shorts or opens going to the wiper motor connector. Based on the host of issues I was having was pretty sure it must be some sort of wiring issue.

Finally solved the problem once and for all by installing a rebuilt motor. If I had to do it all again I would drop the coin and get a new one. But I was locked in with the rebuilt one, had to change three of them out in a row before getting a good one. But that was because of truly awful workmanship of the rebuilt motors (avoid Advanced Auto Parts).

Hope this helps,

Paul