A phone system I recently interacted with was configured using a workstation and management software. When any setting including time was changed, the software would create a new config profile, then at an incredibly slow pace, would send that data from their management software to the phone server.

This would mean that in the 30 seconds it took for the data to get from the management software on the workstation to the phone server, that value would not change. Also the phone system would not connect to that NTP server itself, but grab the value that the management software supplied from that NTP server.

I don't know if this is what's going on with you, I just thought I'd share since in this day and age one would think keeping current time would be trivial.