Ah - you are experiencing "Interior Detail Seat Back" syndrome or IDSBS
This symptom first occured when I had my car detailed years ago.
If you try tilt the seat forward, and don't unlatch it first, then try reach down and use the recline lever to tilt all the way forward, the hinge/lock somehow jumps out on the one side.
You need to play with a combo of recline lever and seat back latch actuation to re-click the unlocked hinge.
I now tilt both seat backs forward using the latch before I nad the car over so the don't manhandle them forward while vacuuming.
I should add that I get my car "detailed" once every 15,000 miles - so I have reduced the risk to my seat backs substantially
