Rear Passenger Buckle Part no. 3513672 or 3513668

Hello there again, still on the search for a seat buckle.

In particular, Part no. 3513672 or 3513668. I believe these buckles were from a 740? Currently have a seatbelt latch from one installed in my 245 in replacement of the original, without a working buckle.

Had one working but accidentally caused it to fault, so a huge leap backwards for me. If anyone knows how to correct this fault, that'd be much appreciated thanks!

FAULT: Buckle won't latch.