Man, there’s just 1 single point where that circuit is open. Just a big series circuit. Sometimes the trick, if the way you’re bypassing the circuit to run backfeeds from the other direction, is to pull one end of the field wire. At some door lock you’ll have voltage and the next you won’t. 99 times out of 100 it’s something in one of the interlock boxes but in the 1 case that it isn’t, the most you could have to do is pull 1 length of wire from one floor to another to bypass an open you can’t see. I’m afraid you were advised poorly.