I have 3 2485-222 Hidden Door Sensors (V.45). All 3 correctly change when the door is open or closed, but one of them NEVER sends a heartbeat ON or OFF message. The other two send infrequent heartbeat messages. I have written a program to capture if the heartbeat is switched ON or OFF from all 3 hidden door sensors AND four 2852-222 leak detectors. All devices, except for the one hidden door sensor will either sent a heartbeat ON or OFF about 1x per day. I have factory reset the hidden door sensor, changed the battery, tried reprogramming the heartbeat interval, etc. and nothing seems to be able to make it send a heartbeat, but, it apparently works fine at reporting door opening and closures. Any advice on this?