XPT Problem

[houston]

One of my 4 button XPT switch controllers after a number of years of reliable operation has begun to send sporadic stray "all units off"; occasional "all lights on" as well stray off and/or on signals to individual addresses. This includes addresses not assigned to this controller. In addition one of the 4 addresses assigned to this controller no longer responds to manual use of the switch while the other 3 continue to respond appropriately. There is no identified noise that could be the cause.

An identical XPT switch on the same circuit in close proximity is assigned the same addresses --- operates properly and does not send false signals.

Is there any solution to this or does this indicate a defective switch which will have to be replaced?