Well here I am again. Can't seem to stay away long. Axxess system 9.1

Last night our Frond desk phone started acting strange.

When a call comes in (8560 phone) Call 1 lights up staff answers call.

Next call comes in and only displays on panel then disappears. If you end original call, Call 1 lamp lights up and phone rings.

Previously, Call 1 lights up, answer call. Next call comes in and Call 2 lights up and rings.

What could have happened that this is now occuring? Is there something in programming I can do to fix this? Or is this something at the carrier with rollower lines?