Poor downstream with high errors causing issues with connectivity for both internet and voice

I have an Arris T25 modem. It disconnects a few times a week. This is a problem because I use voice heavily. I am a medical interpreter, which you can imagine I am quite busy. I can't have random disconnects and calls being choppy when I'm interpreting for Covid-19 patients or their families in a hospital or emergency situation.  One interesting thing is that the Xfinity XB3 showed that the modem was locked to 24 downstream channels withthe the other 8 not locked. This modem shows all 32 channels active but the signal drops off a lot around channel 24 from -6 -8  on channel 1-23 to -9 to -12.8 on channels  25-32. I moved the modem to another outlet that is on the otherside of the wall from the xfinity panel coming in to the house and I can get the value down to -10.3. There was one time during the troubleshooting process that they activated the Arris t25 and it only showed the 24 downstream channels and wasn't locked on to the other final 8 channels. Downstream was between -6 and -8 on channels 1-24. Internet worked but phone only worked for the test call and stopped. At that time, cable interface was up but EMTA was down with failed provisioning listed in the logs. After the CS agent reactivated everything it was back to being provisioned for 32 channels. When I moved the modem back upstairs, the modem was all the way up to -13 on the highest channels. The Xfinity gateway does not restart and I have been in touch with Arris and they even sent me a replacement modem and it is having the same issue. Two modems would not be bad. Comcast said they can't send a tech because of Covid-19 even though I'm certain if there is an issue, it's outside because this just started happening after using the Arris t25 modem successfully for four months. What did the first CS agent do when he activated it so that the modem was only locked on to the first 24channels just like the Xfinity XB3? I am scheduled for a tech to call me on Thursday but thought I would post something here to narrow down what I should tell the tech. I am also getting this messages in the event log, each time the modem restarts.