Intermittent T3/T4 timeouts

I’ve been experiencing intermittent full loss of internet with my modem indicating lots of T3 and T4 timeouts.  I replaced the modem since everyone seems to blame it but the issue is still present. Tonight when the modem couldn’t get back online I brought the modem outside and tapped it directly to the feed line coming into the house and the modem struggled to connect.  After 10 minutes it synced in fully bonded, but then dropped out again after a few minutes.  When I brought the modem back in the house just hoping it would come one line and stay there it locked in for a few minutes but upstream only bonded 1 of 4 channels then after 5 minutes I was offline again.

Interestingly, the modem showed almost zero downstream correctable and uncorrectable frames for almost 3 days, and then today it shot into the millions with my devices showing logs of going on and offline consistently throughout the afternoon.  Online support just wants to blame my modem, but if the issue still shows up when I replace the modem and tap directly into the incoming line, what’s the next step to get this resolved?