The seatback (recline) will go forward but will not always go back. I thought it might be the switch but it tested fine. I got the seat to recline but when my friend was riding in the seat he said it moved back to a straight up position while he was sitting in it and he claimed he didn't touch the controls. I removed the switch and tested it again, it all looked fine. I got the seat to recline and removed the switch. After a couple minutes while the vehicle was sitting it moved back to the straight up position with the switch removed. Where should I go from here

 

Year/make/model?