I've experienced the same problem as well, but as of tonight all seems very well with no breakup of OTA HD channels. However here is what I observed during my troubles:
In my case the pixelation only occurred when tuned to a high-definition OTA Channel. When I switch to any of the OTA SD sub-channels, including any of the SD OTA Channels of a problem OTA HD channel that was breaking up, all was fine. This got me thinking.
Perhaps one of the earlier updates messed up how the MoCA handles the much larger mpeg-2 data used by OTA. OTA high definition channels are using much more data in much larger files using MPEG2 and this could explain the pixelation if the MoCA system was somehow screwed up. However the OTA sub channels are highly compressed MPEG2 and that data passed along very well for the clients with no break up. Of course Dish Satellite HD uses mpeg-4 and so the smaller files and fewer data don't end up with a pixelated video. Also, Dish SD channels on the WA still using mpeg-2 are so highly compressed anyway they won't be challenging to whatever messed up the MoCA resulting in a steady picture with no break up.
In my case it seemed the big Nets and a few other HD OTA were being pixelated on some of my Joey's while other OTA HD channels were not and this difference could be due to the fact each broadcaster sets their own specific parameters when encoding such as how much compression and how much forward error correction, etc., which can result with a steady OTA HD picture with no break up while the other OTA HD channels do break up.
I should also add that the Diagnostics menu showed all of my MoCA connections to be strong signal during this period of video break up for OTA HD.
This effect is similar to what I have encountered using WiFi to watch mpeg-2 on an older devices using Video LAN regardless of which band I use. Whanever watching my own MPEG4 viedo or Dish Anywhere or Slingbox or anything from YouTube no problems because they are encoded with mpeg-4 or other equally efficient encoding. Meanwhile when I attempt to stream live MPEG2 content from my servers using my WiFi on my older devices I sometimes get stuttering or stops and starts and this is only when trying to stream mpeg-2 files via wifi to my older devices. my newer devices simply don't encounter this problem and stream mpeg-2 video from my servers with absolutely no problem. And for what it's worth I have an extremely capable WiFi network and fully gigabit LAN. it's not my router nor my LAN.
Well that's just my observation and theory but again so far as of tonight it seems I have no problems watching any of my OTA HD channels via dish using my dual tuner OTA dongle on at least one of my Joeys that was giving me break up problems for OTA HD. I have not checked my Hopper with sling for the latest software but I did get new software it a few days ago that took away the infamous no longer to edit a label of the channels Etc and I don't like the takeaway of those features.
Finally, all this was when I was watching live TV not previously recorded shows. I do believe the break up when playing back previously recorded shows on OTA, even the SD OTA, is a separate problem because I was able to watch that very same as SD OTA live with no breakups. However all of it was a very vexing Troublesome problem in our household.
Hoping a fix comes to everybody else, a good day to all.