Originally Posted by Kev

They have changed something as the new ones don't suffer from the problem.

I do think in some of the cases the actual terminals were the problem with low tension on them, causing resistance, melting of the plug ETC.

I have seen some Z's with water ingress in the rectifier plug where the seal has failed to seal. So there were a few problems why the Z would not charge.

As mentioned we have not seen any repeat failures