Gigabit connection/speed issues with multiple modems

Modem(s): Netgear CM1000v2 and Arris SB8200

Same issues on both modems. T3 and T4 errors in the logs, have not achieved anywhere near gigabit speeds (topped out around 360mbps), multiple disconnects throughout the day.

Both myself and my wife work from home at this time, so connectivity is key.

I have gone through all of the troubleshooting steps in the sticky. Watched the youtube video multiple times. Gone through checking for splitters, used two different two-ways and a three-way with a cap. Even went to so far as to buy another $200 modem and have all the same issues.

Had a line tech come out Monday and inspected from the pole to the house (cannot come indoors, SE Michigan). Other than an indoor filter and a loose connection in the outside box, he said there should be nothing wrong with my connection from out there.

Prior to resets today, there were a lot of UNCORRECTABLEs as well, both OFDM and downstream channels.