R380 reverse gear popping out

Hi

I have D90 300tdi with a R380 and the reverse gear keeps popping out, all other gears are fine, have replaced the bias spring and setup.
I have checked the reversed light switch and all good!

Any ideas?

has it been tricky to engage for sometime does it feel like its going in fully?
reverse gear dog teeth are very prone to wear,they are coffin shaped and the head end get chipped off, its those bits that hold the gear in engagement the same when you hold the stick in a forward gear and accelerate you can feel the stick trying to engage further,rev gears is the only gear you normally expect will need changing when rebuilding a box, it could be the synchro unit but youd probably expect 5th to show some symptoms when trying to select

Hi

it’s fine going in abs stays in while I reverse but if I stop and continue to reverse it then pops out.but 5th gear is fine. Sounds like the box needs removing abs stripping down!!