Based on this I believe Bob either has a malfunctioning EZIO6I, or firmware 25 has a bug in it. It sounds like he should send it to SimpleHomeNet to get it re-flashed with the latest version and tested, correct?
Updating the firmware cannot hurt. The update can be ordered online. It will either fix the problem or eliminate the EZIO6I as the source of the problem. I believe the EZIO6I I have with v28 firmware is the latest. Bob should double check the wiring that is placing GND on AN1 and AN2 and he should set the Analog Trip points to the values I suggested in earlier posts before ordering the firmware update.
If you have access to a Windows OS and can connect the PLM to a port on that system I would recommend installing the SimpleHomeNet Utility Suite (free download software) to verify the EZIO6I configuration before ordering the firmware update. Also if you have a meter check the voltage between GND and +12V to get a reference measurement. Then measure between AN1 to +12V and AN2 to +12V to confirm the same reference voltage on both analog terminals.