Blizzard front diff, keeps coming undone

[Swerving]

Hi,
I have as title suggests a Blizzard, built from a kit, I have had continual problems with the front ball diff coming undone, ie the screw that goes through the entre of the diff into the brass threaded fitting keeps unscrewing, causing only 2wd and terrible handling/steering issues.

I have tried blue threadlock but that does not seem to do the trick, I have also tried different amounts of torque on the screw, ie tighten it as hard as I can, or juust leave it not 'fully tightened'

Anyone got any suggestions as to building these diffs and how to stop this happening?

The rear one seems ok and doesn't undo now.

Peter