I will eBay the R-Tech now as I'm reasonably confident that it is a fully working unit.
Sounds like wire slipping in the rollers (incorrect groove selected) or tip seizing on the wire (wrong size tip, not tightened in tip adaptor, overheating or a combo of the aforementioned etc)
Or, badly wound wire disappearing down the side of the spool or caught between layers and not feeding off smoothly or jamming. Either way the problem sounds 'mechanical' to me.
I meant to type 20 defective spools out of a pallet load of 72 in total, all of the same batch. And all to the same customer. No further instances before or since.
What was the manufacturer/supplier's attitude to the problem?
I agree, not something you expect from a decent machine. Had it been a cheap Chinese one then that is different.