Everyone is making the assumption that the stringer is using the machine to tighten the knot. However:
Originally Posted by Luiz.Melao
He says that after he ties the knot and the machine pulls the string, the string just gets destroyed.
This could just as easily be describing someone who starts the crosses with a starting knot.
Luiz, you should seek clarification on when the breakage occurs. If he is tightening knots with the machine, ask him to do it by hand. If he is using a starting knot for the crosses, ask him if he can use a starting clamp instead.