Took the autolockers off to see what went wrong with one of em. Cant find a particular cause so I suspect they are just worn out. It probably does happen eventually.
It wasnt the circlip Ste, You know the autolocker has a cutout which is supposed to be centred, well the locker has slipped past the cutout and jammed.

I suspect it may just be worn out. Although I tried swapping the 2 halves over from one locker to another and it continued to do it. Both look to be in the same condition so not sure whats causing. Everything else appears to be in good nick with no missing splines or anything.