The passenger seat adjusting control will lock when it is moving the seatback back. Sometimes it will not work moving back at all. It will move the seat forward, but then it locks forward and will not move back.
The front passenger seat adjusting control locks. on 2006 Hyundai Azera
There was a recall on the passenger seat. Check with your Hyundai dealer about it. I had some issues with my passenger seat. It took a while but Hyundai fixed it. Everything was covered under warranty. Hope this helps.