viper 211hv randomly stops responding

Hello everyone... I've searched through the forums, but could not find anything close to what I've been experiencing. Any help or suggestions are greatly appreciated. I have a Viper 211HV keyless entry installed on a 2007 Ford Taurus [FYI, the 2007 uses same wiring diag as 2006]. The keyless entry 'unlock' function will randomly stop responding to the remote. Sometimes a few hours, other times days later. However, as soon as I manually unlock the door, open the door, then close it, the unlock function works fine. When this problem occurs, the 'lock' and 'trunk activation' features of the alarm still work fine... but unlock will not. I have read on the forums, and didn't think this could be a diode isolation issue since it is keyless entry only... so I am stumped. Anyone ever heard of such a problem??? Many thanks in advance...

did you test the unit? ie at the times when it won't unlock is the unit sending the pulses?

I have not checked with a meter. I had a different alarm about six months ago from Summit Racing (don't remember the brand) and it was doing something similar, so I figured it was a setup issue. I will check though, just to make sure.