Never come across them leaking from the spot welds before. In theory they shouldn't leak because they are a plug weld.
One thing you could check is whether the small breather hole (3mm) in the axle tube is blocked which is causing the axle to pressurise.
Kind regards
Arwyn
I have checked that and it is clear, just to be sure I also put a 2mm drill in and gently turned it by hand.
