OK, interesting progress. I simultaneously recorded "This is Us" on the primary NBC channel (channel 36), and a sitcom episode on digital channel 36-2. At the 9-minute mark, there was a terrible picture drop-out on This is Us. I stopped the recording, switched to the recording on channel 36-2, and there was a break-up
at the same 9-minute mark.
@harsh So, what does this tell us?
Given that 1) you see this on only the one local station not all of them, and 2) you see this in both the Directv delivered locals and locals received via ATSC PSmith's idea of EMI can be discounted. There's no way an EMI source powerful enough to affect both Directv's OTA reception and yours, but narrowband enough to only affect that one channel (RF 21 so not even near the UHF signal boundaries) would go unnoticed.
There are only two possibilities. One, the ATSC signal the station is broadcasting is a glitched, and if so you would see such breakups when watching on any ATSC tuner like if you used a splitter and connected OTA directly to your TV and watched live while recording until you see a glitch, then see if the glitch matches (so there's another thing you can try)
Two, the flaw is in the HR24, where some corner case in MPEG2 decoding is tripping it up. You can figure out if that's the case trying the splitter idea above or hooking your AM21 to your HR54 and see if the same thing happens.
If you determine it is the station's fault, find out the contact information for the station's engineer. Tell him you are seeing glitches when receiving the ATSC signal, and if you can provide him exact times you have seen it that may help. Whether he ignores you, claims you are wrong, fixes it or not who knows. All you can do is report it, and learn to live with it if you are ignored.