I hate to ask. We are a phone dealer, but I have had very limited experience with this PBX. I have worked on the KX-TD1232 and KX-TA824 and even went to a class for Panasonic Kx-ns700g after Toshiba went under.
A new customer can't find a local Panasonic dealer in the area (Orange County, CA). So We thought we would see what we could do to help.

I haven't been on site yet, but the customer says they have a KX-TDA100 with TVS125.
Symptoms: DDS console is not working properly, we are unable to put our phones on “night mode” while we’re not in the office, we can’t check voicemails, and one of our phone lines is down.

I don't think it will matter anymore. Even before we arrived onsite they decided that they want to talk about replacing it with a hosted PBX.

Good to hear! The TDA can be programmed via handset, but it's usually much easier to use the Panasonic software. Same concepts as the NS.