That got a bit complicated but I think you're saying that whenever you write to a servo using your "slave" mechanism to sort out the servo/value then the servo doesn't move. That sounds like a coding problem.
Are you sure all servo objects are "attach"ed to the correct pins? If the write seems to have completed but nothing happens my guess is the routing is mixed up so you're writing to something but not to what you think.
No way to make a better guess without seeing the code.
Steve