there are 4 department groups in an SV9100, 1 stopped working yesterday while nobody touched it. when you rang the department pilot, you got beep. So we re-created the department with same pilot in another department group, it fixed some issue, at least we could ring the pilot.

This morning they had another issue:
"Extension 363,364,365 when all 3 phones ring with the same call, if you answer the call on one of the extensions the call continues to ring on the other extensions , you cannot answer the other phones if you do you interrupt the call being answered.
Once the call is finished the other phones then stop ringing."
by the way, 363-365 are in the department.

It's weird. Any idea?