In Unison systems with portable station connectors, if the EMI Filter/Varistor 220pF 25v (L1) is damaged on the portable connector; the ULP supply will no longer output +21Vdc and -21Vdc (like it should).
It will now output approx. +42Vdc and -0Vdc. This will cause all attached stations to not bind or become unbound. If the portable connector is removed, the system will operate normally.
In this case, the portable connector should be replaced.