Valiant convertible driver seat issue

I'm going with warn out parts. my 67 Dart has a chunk of plastic that sits on a metal pad on top of the seat cover in the area you have a leather strip? (BTW the strip does not look stock but maybe if it is a 66 and older who knows) That is the stop on my car.

in other words the warn out pivots points and holes are allowing the seat to ride over the Leathers pad/ back of the seat bottom when some pressure is applied. ALSO the inside bottom of the seat back might be broken allowing for movement.