The defrag seems to have helped the recording process.

Last night during multiple records, there was no pixelation within the recorded files that I've so-far been able to verify. I have a couple more to check out still.

Another (unrelated) problem did come up though. One of my tuners now fails to tune one particular channel, while it remains perfectly functional on the other tuner. This has happened before and went away after a reboot I think. Testing that now...