Rear diff issues

[jjsaul]

I'm trying to sort out my rear diff lock.
Previously had discovered the diff lock selector fork was mounted upside down - over the last day or two I have stripped out the rear diff and cleaned everything up.
Now reassembling it the movement in the fork / sleeve doesn't make sense - in the 'engaged' position the castellations on the sleeve mesh nicely in the diff, in the 'disengaged' position, it doesn't retract far enough to clear them - to me it should move far enough otherwise when you try and drive it will just smash the sleeve to bits (or something else).
At this point the sleeve is NOT bolted to the diff lock actuator shaft so has free movement within the diff casting along that shaft, but it fouls the diff casing casting before the sleeve is free of the diff gear castellations.
I have looked at the parts diagrams for front and rear and they're completey different so someone hasn't shoved a front one in the rear by accident.
Photos in 'engaged' and 'disengaged' positions achieved by sliding the fork and sleeve across by hand.

Any ideas people??
TIA

 

[jjsaul]

Also, should the selector shaft go right into this hole in the casing? Mine doesn't seem to fit (with 2 seperate actuators, so I doubt that's the issue) - it only sits just up to it and won't slide inside.