Omnipro 2 - zones and loop value too high?

One of my doors won't chime when opened. PC Access shows a value of 250 for the Loop (Show->Status->Zones) when closed, and 253 when open. The rest of the doors show 148 when closed and 253 when open.  I've replaced the sensor, but the door still won't chime, and the values didn't change. I even tried shorting the wires at the door.  I haven't tried shorting the contacts on the board, because there are resistors in-line with each of the sensors.
 
Any advice on troubleshooting?
 
I haven't found a place to adjust the sensitivity for open/closed...
 

Welcome to the Cocoontech forum @Remen.
 
Disconnect both sides of the 2 wires used in the zone and use a VOM to check for continuity.  One wire might have stretched to breaking.
 
There is no place to adjust the sensitivity on the OmniPro 2 panel.  Just an end of loop 1K resistor is used for the panel.