Drop the windshield. You have to undo the torx bolts on the visors, two torx on the roll bar to windshield on each side, and a plate on each side with three torx each.
Now you'll see the motor. Unbolt it and you should see the output shaft with a 360 degree swivel. Likely, there will be a nut on the tapered and keyed output shaft with a metal elbow in there.
You probably have stripped teeth on there. With mine, I had to go retard tight with an impact because it was completely stripped.
Before doing that, Make sure the motor is in the rest position. Turn the wipers on and off so you know the motor is there. Then tighten the metal elbow in a straight line with the wiper arm inside the windshield, and reattach it to the arm.
Assembly is the reverse of removal... Do yourself a favor and get some 5/16-18 hex bolts at Home Depot (coarse thread) about an inch to an inch and a half long for the roll bar windshield mount. I never put a torx back in unless it doesn't have much torque on it or it can be easily removed with vise grips if it strips.