The Dex 210 diff is a flipping nightmare.
I built it first time - no problem.
After that - lousy - I had to get the gear diff - I am sure that the ball diff is a ploy for you to buy the gear diff!
I have purchased answer ceramic balls and the ceramic thrust bearings. Still lousy. changed the circlip (and yes I used the right pliers) still nothing.
I am no idiot with diff building having done plenty of 1/12 diff builds, and am, believe it or not, known for my diff building in the on-road world.
That's my rant done with.