Well, my upload speeds are too slow to upload even a half hour episode of HD (~3.5GB). I've recorded ~10 minutes of SD TV and can reproduce the problem on it, although it isn't as bad. I'll try to upload it in the next day or so.
I can tell you that all of my recordings have the problem in NextPVR but they all rewind, fast forward, and skip back/forward OK in Plex and WinTV 8.5.
Thanks