error 79 on whole house

Our whole house system has never worked correctly.  We have a hr24 and a hr22.  Many tech calls but the swm signal strength has zeros which vary in number of zero readings.  The techs have changed out the hr24 the black box the swm switch.  Any ideas as what to do next? The program from other receiver will start to play back and then say THIS RECIEVER HAS BECOME DISCONNECTED FROM WHOLE HOUSE SYSTEM.  Sometimes it will restart on its own but when it does it will start over on the replay.