After the velcro stiching came loose I bought some snaps on amazon and installed them at positions equivalent to full tension on the strap. Really simple install and so far haven't popped out once in 8+ months.
Sounds very similar to my driver seat. The main seat height adjust motor will make noise (different from all other motors) but no movement in the seat. What I found after I removed and disassembled my seat was that a nylon gear inside the worm gear drive was stripped and the motor was just free...