Have you tried changing the ntp mode to manual, this is required in case there is no ntp addresses configured and you are using default tandberg ntp.
Reboot the unit once you set the correct time and time zone and chaning mode to manual.
NTP does not reflect the timezone at all, all servers worldwide just return the UTC
and your operating system then does the magic on mapping that time to your local time.
This sounds either like a bug (but I would assume that more people would have complained
about wrong ticking clocks :-)
Or something is changing your setting, like TMS, a set up external manager, some control system
(via ip, web/telnet/ssh, serial). Not sure if the endpoint supports it but there is even a definition
of setting the time zone via NTP
At the web interface uses the api I would not beleve that it makes a difference, but try
ssh to it as admin and set and check the timezone from there.
xConfiguration Time Zone
you can check the timezone the output shall be something like:
*c xConfiguration Time Zone: GMT-05:00 (Eastern Time (US & Canada))
xConfiguration Time Zone: "GMT-05:00 (Eastern Time (US & Canada))"
you should be able to set your timezone.
One test could be, set the time and the timezone and disconnect the serial and network cables,
if it still shows the right hour you can be sure that something on the outside triggered it :-)
Looking into the logfiles might also be interesting.
Please remember to rate helpful responses and identify