This system was installed May of this year. Cooling performed great ...no issues

Since the heating season has come and on 3 different days... one zone (same each time) runs wild and overheats

Let me set this up as to what I know from the customer and picutures they sent along and what I suspected and checked

3 zone wireless ( no outside RF interference suspected as customer who is qualified in the field of alarms knows his house)

no call for heat on all zones, all in heat only mode

heat pump is off when this happens

customer was not interfacing with control

fans on continous all zones

zone panel displays no call for heat of any type, on any zone, damper open on the zone that runs wild, other two are closed

aux heat is lock out until 35 deg f .... we have been above 35 when this happens, I tested and proved

thought it was not terminating defrost properly , checked and proven 3 times in a row last visit

So what happens the zone in question
-Damper is open
- other 2 close
- fan ramps right up
-electric heat strips energize
-no call for heat set point @ 68 room got as high as 80,
- only way to stop is to kill the power to AH and after its reenergized
system returns to normal operation.. AC even came on when the zone was in auto mode to cool the room
any ideas as to where to start ... I am not a parts changer

thanks