It doesn't happen every time, and it's difficult to narrow down what is causing it. I thought it might have been a faulty MicroSD card because it only seemed to happen when recording video to SD. However, the replacement SD card does the same. I think there may have been a few instances where it happened when I recorded video to the phone also, but I hardly ever use this setup. I can't say that recording to SD is the root cause.
During video playback, the stutters are still there in exactly the same places, indicating they've been recorded during the video.
Has anyone else experienced this with a 820/822?