FALSE ALARM FROM DOOR SENSOR

Armed my system at 8:27 pm

REAR DOOR sensor has "communication failure" at 8:49 pm

REAR DOOR sensor has "communication restored" at 1:35 am

ALARM at 1:36 am "rear door opened"

Rear door "Open& Closed" at 1:36 am

Rear door "Open& Closed" at 1:36 am (yes this shows up twice)

DISARMED at touchscreen at 1:36 am (by me)

QUESTION:  It was my understanding that a communication failure could not cause an alarm.  What caused this one?

I've had this system for a long time and this is our first false door sensor event.  The door was closed and locked when I found it.  My cameras showed no activity.  It was a true false alarm.

Thanks

Tim