I'm struggling with trying to re-assemble the parts of the tailgate lock on my 1990 Discovery 1, 200Tdi after examining the springs in the latch . I'm very grateful for the parts diagram at post #8 in this thread. Part 15 is a small black plastic part to connect 17 to 13. I have some queries...

I've owned my 1990 200TDI Discovery for 23 years, and the tailgate lock has just failed, so I can't complain. Symptoms are that the tailgate will lock and unlock from the driver's door central locking with the key. The tailgate will lock with the key in the tailgate door, but it will not unlock...