The dial opens one side of the line for pulses. The other switches close to shunt the receiver.
So that doesn't make sense.... I thought you were using an ITT network, but with so many posts...
Do you have a millimeter? Or continuity tester?
What I would do is check hook switch contacts, dial contacts, etc. Then check for a potential to everything else to see if something has grounded, or shorted to something else.
Then connect the bare essentials to power the network, and check for stray voltage to other places.
That is odd, sounds like you have tried to isolate everything, but something's still an issue.
Good luck Harry.