I have a customer set up with a DS2000, 2 Station cards filled to X. 327. Friday X. 315 goes dead for no app. reason. I swapped phones, swapped cards, reset the system, re-punched wiring, and tested the phone right at the system, no luck. I have a slow flashing yellow on the card when no extensions from 300 to 315 should be in use. Change the punchdown to make it X. 327, and it's fine. Try a swap extensions (327 for 315), and it fails. Any ideas??

have you looked at 1801 to see if a phone is installed for the port ?

What version software?
If you disconnect all four RJ45 connectors from the DSTU card does the yellow led go out?

They are an hour away, so I will check both of those suggestions when I truck up there this afternoon. Thanks for the input!