I experienced something similar; the windshield wiper was stuck at a 30-degree angle and wouldn't move. While the wiper was still running, I couldn't make it return to its resting position or move forward. I was only able to force the wiper back into its resting position manually, without it moving.
Yesterday, I finally got around to fixing it. I removed the wiper arm and turned on the car. It moved slowly, but correctly back and forth. Then I put the arm back on, and it worked the same way. I lifted the wiper blade away from the windshield, and it moved.
Then I removed the wiper arm, applied some creeping oil, and let it run for half an hour without the arm. For now, it's working again, but I don't think it will last. I'm having some problems with the windshield wipers anyway; I also had to replace a new rod in the front. And that's for a vehicle that, in my opinion, is still quite young

.
Soon, I'm going to get a new motor because I want to switch to flexible windshield wipers, and the motor's mounting position on the wrong side makes that difficult.