I have a Siemens 3500 that will drop power (a quick off and on) when everything comes back up they will notice that the phone time will be off. Usually it will be around 30 to 40 minutes slow than the actual time even though the phone system was not off that long. The phone system should be on UPS so it shouldn’t reboot anyway. The software is version 4 anyone know why it would periodically power down and back up?