OK, I checked the firmware code, and here is the logic:
– when special station auto refresh is turned on, the master controller sends a command to turn the remote zone on for 2*MAX_NUMBER_STATIONS seconds each time. As firmware 2.1.7 allows a maximum of 56 zones, this is about 2*56 = 112 seconds, so roughly 2 minutes. And every MAX_NUMBER_STATIONS seconds (56 in this case), the master controller send refreshing signals to renew the on time for another 112 seconds. This keeps the master controller and remote zone in sync as close as possible, so even if master controller loses connection to remote, the remote zone will remain on for no more than 112 seconds.
– when special station auto refresh is turned off, the master controller sends a one-time turn-on command to remote zone, to turn it on for the maximum number of time (about 18 hours), and will not send refreshing commands. It then sends turn-off command when the zone is scheduled to be turned off.
If you observe the remote zone turns off after 2 minutes, even if the corresponding zone on the master controller shows longer time, that means the master controller is not sending renew commands for some reason. I don’t know why, but my guess is that maybe it took master controller more than 112 seconds to cycle back and send renew commands — however, even in that case, I would expect it to again turn the remote zone on after some time. So basically I don’t know the reason, however, it sounds like keeping special station auto refresh option off resolves the issue.