OP
Silly Sausage
a lot of it is prep though Archy with crimps...as with most things..
you can always bare off too much copper when prepping a cable end for crimping....so you cant get a purchase on the other cable your crimping to (when extending)....so basically it just pulls off....now i`v come across this one a few times when inspecting C/Us....should always perform a `tug test` on these whenever you find em when on an EICR....
Yeah, alright, but it doesn't take much effort to work out how much to strip and butt crimps have a 'stop' in the middle anyway.