A 126,000 Parker should have no "wedge" unless it was retrofitted. You will have to tell us whether this is the case. Put a piece of electrician's tape on the back of the forend lug, reintall the forend, and see if the looseness or "click" goes away. If it does, a more permanent shim soldered or epoxied onto the forend lug will be your simple solution. Hopefully the locking lug is not loose in the slot, a more complicated fix.