Kinda confused, is the voltage off on can low. The only thing between can high and can low is your 60 ohm resistors. If you have a short to voltage or short to ground on either line it will affect both. Also it’s not super difficult to unplug nodes off the circuit one at a time to find you culprit. Unplugging one node should not take the whole circuit down. If you have one bad node it will take the whole network down however. More times then not a node will be shorted to can voltage vs a bad cable. It’s pretty easy to tell tho, you can ohm a can line to tell if it’s bad. And I’ve built more then one can network out of wiring, alligator clips, and resistors to rule out any wiring/connectors. Not anything I’m gonna take a picture of cause it didn’t look great but it works.
Did they verify the can voltage at the can driver?