The wiper linkage is bad. Or the wiper arm stud bushings (where the arms attach to the cowl) are rotted out.
The linkage is connected by plastic bushings and with age they deterioate.
The linkage bushings are worn/missing/broken or the wiper arms are not timed properly to the wiper transmissions.
Rockauto.com has them and so does O'Reilly's auto parts A Chrysler dealer should be able to get them.
You have to remove the linkage from the wiper motor.
There are plastic bushings on the wiper linkage that wear out and cause the erratic movement. Chrysler does not list the bushings and will recommend buying an entire new assembly. Don't, go to NAPA and they will have the bushings on their "HELP" rack. I went to NAPA and they only had ones for Chrysler which are different then the jeep. I went to Canadian Tire in Toronto and found a variety pack of the bushings in the self help area. They were labelled "wiper linkage bushings." Since they dry up and burn out, I applied a dab of wheel bearing grease to the inside to hopefully prevent that from happening ever again. The whole process was fairly easy, I found channel lock pliers the best to remove the old bushings and install the new ones. Hope this helps. Carquest, Part #49445. Manufacturer is named "HELP".
Check eBay for the plastic linkage bushings. They are not available from the Ford dealers.
Transmission linkage bushings can be put on by first removing the linkage cable and removing out outer linkage cover. The bushing can then be pull out and replaced with a new one.
Its a dealership part
Binding in the linkage, bad windshield washer motor
If the linkage is not loos or damaged, check the linkage bushings for wear. If the bushings are not worn and the linkage is properly adjusted then the problem is internal. the shifter bushings, rods and shifter forks are probably worn and need replacing.
Linkage bushings on wiper arms coming off back side of wiper motor under cowling