The symptoms might by caused by a bad cable box or a problem at Comcast (check https://www.xfinity.com/support/status/, 1-800-Comcast voice response, or the "My Account" app) but are most likely due to a poor connection between the box and Comcast's network, usually in or near your home.
Troubleshoot by checking all connectors for corrosion and tightness, and by looking for damaged coax cable. Running the cable through a surge protector, a defective splitter, or too many splitters can cause signal problems as well. If there is an amplifier in the line make sure it's getting power. You might also try unplugging the cable box/DVR/digital adapter power cord for a minute or so.
If you can't find the problem, call them at the phone number on your bill or 1-800-Comcast, or chat with them using the TV Support option at https://support.xfinity.com/chat. Ask them to check the account setup and send a refresh signal to the box. If they can't fix the problem remotely, insist they send a tech out to identify the cause and correct it.
If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan (https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast cable box/DVR/digital adapter or anything outside your home, you shouldn't be charged.
Well, I get the same type of dvr artifacts upon playback, being able to reproduce them on the same part of a recording, and this happens on most recordings some more noticeable than others. However, I can usually get perfect playback within the house streaming to my IPad.
i have also gone through a few remote sessions and have had a tech out to look at the problem. We went to every cable box, checked the connections between them and the in-house Comcast amp, power cycled all the boxes, and the problem still remained, all while the signal levels all showed at acceptable levels on all my boxes via his smartphone display (not available to customers I guess).. Since he could not find the cause of the very visible problem, he also told me to call in and cancel his appointment (!!!) so I would not be charged the $40 for his service call. He basically said to wait until it goes away as it may be on Comcast’s end, but it has not after a few weeks.
So should I just try another tech who may be able to solve the problem or is there a better way to proceed?