I was having similar issues to these errors you are seeing as well.
Basically whenever T3 time-out would happen my internet would cut out for a brief moment. I'm of course not an expert but along with having the tech coming out (3 times) they replace practically everything (the connectors, splitter, modem, checked all lines and even checked the connection at the poles.
A fellow community member "b-slice" offered the following prior to calling into comcast that may help in this case.
"Start monitoring your upstream power levels. When my issue was happening, the UPS power level were fluctuating up to 50dBmV or so... "
So to recap my situation: A 2nd level tech came out and saw that the original tech actually just ran a new line into my room while still using part of the "old cable". It turned out the "old cable" had some punctures from the carpet nails which most likely was affecting my intermittent disconnects. It's been a full day with no issues thus far, but the true test will be during the weekdays when I'm online working from home and during my web trainings to see if this fully resolve.
I'll post back on Monday night to share in case this ends up helping anyone.