Image Sync Distortions from tape on NBSC Player

[Gunier J. Kintgen]

Hello! So, I've been experimenting with recording NBTV signals onto audio cassette tape, with general success. The pictures I'm getting off the tape look good, but there's one problem: On some parts of videos, the sync locks on at seemingly random parts of the image. I've attached a WAV file containing an NBTV signal showcasing what I mean; It's the music video for We Can Work It Out by The Beatles recorded to tape, with standard 32-Line video encoding. Pay attentions to the close-up shots of Paul, that's where the effect is most visible. My theory as to what's happening, is that the software is confusing the black parts of an image with the sync signal, causing the alignment to go all screwy. I've noticed it only happens with the black parts of an image, which leads to my reasoning. Does anyone know for sure what's happening, & maybe how to fix it?
Also, while I'm here, Does anyone know why the color bars at the beginning look so unintelligible? Do you have any tips for getting a better image off tape? Thanks!

-Gunier J. Kintgen, Your Pal.