I'm just reporting an experience, not some sort of magic resolve.

We installed a "self install" Internet, (2) TV setup shipped to a customer. Internet was fine, but the TV's had extreme video blackouts, lost audio, and pixelation every few seconds. We called Comcast support, couldn't resolve anything during the call, and a technician visit was scheduled. Mysteriously, about 10 minutes later the issue mostly cleared and we saw only one brief picture stutter in the next hour or so. Over the next two days no issues were observed by the customer.

Then the technician arrived at the condo. Prior to the technician entering the unit, both picture and sound disappeared. The technician claimed to have installed a MOCA filter at the drop. This is a high rise condo. Over the next couple hours the technician struggled to restore the picture, claiming bad MOCA issues (according to his codes). The technician worked through several agents of various levels, without being able to resolve the issue. Both the Gateway and cable boxes were replaced during his struggle. Finally, after rearranging our wiring, the technician left, claiming "bad wiring".

After the technician left, we restored our wiring to the original and started working through TV and cable box menus. This is a SONY TV and, while it's likely a coincidence, after flipping Brava Sync (Off-On), the picture returned with no further issues.

This could have been a coincidence as someone at Comcast central continued to fuss with things. My thought is that during the initial configuration MOCA synced with another condo's MOCA, this connection was broken when the MOCA filter was installed, and our customer's units would not give this up -- hence "no MOCA" for our customer's units. Further, I speculate that additional diagnosis was complicated by central automatically installing the old network details into the new replacement units as a convenience. Likely, at the original install (without the MOCA filter) our cable boxes attached to the first MOCA responder, which was a neighbor's system. I speculate that the issue probably resolved due to a timeout or action at central, not because of my fussing.

Everything you said sounds reasonable. And could be a proper explanation about what happened.

I will say it was a mistake to have installed the system originally 'without' a MoCA filter to begin with. You should never do that. MoCA 101.
I keep a bag of them on the van, they are cheap.

Your post highlights a problem we have all been dealing with for many years now. Everything is software driven these days. Many times we have no access to and are not allowed to diagnose or program the devices that are installed everyday. Everything is built to be plug-in-play and when that doesn't happen, people in the field (installer & customers alike) often have no recourse to do anything about it.