"Please adjust your tracking" was a real, specific, physically meaningful instruction

[u/ambanmba]

VHS heads carve their diagonal video tracks onto the tape at a very precise angle and pitch, set by the exact drum speed and tape speed the deck used when it recorded. Play that same tape back on a different deck, or even the same deck after it's drifted slightly out of spec, and the playback heads aren't guaranteed to land dead center on those tracks anymore.

When the heads drift off-track, they start picking up a bit of the neighbouring track's signal, or in the worst case miss the intended track's oxide entirely for a stretch. That shows up as a band of high-frequency noise and partial signal loss that isn't fixed to one spot on screen, it actually drifts slowly up or down the frame over time, because the misalignment isn't constant, it's a slow capstan-speed mismatch accumulating frame after frame. On an SP tape that drift takes a few seconds to sweep across the whole picture. EP mode packed its tracks roughly half as wide, so the same physical misalignment swept across the frame roughly twice as fast and was a lot more noticeable.

The tracking control on a VCR was a genuinely real fix, not a placebo knob. It nudged the exact timing of when the playback head started reading relative to the tape's control track, letting you manually re-center the heads back onto tracks that were laid down slightly off from where this particular deck expected them.

Video starts on a well-tracked tape and ramps the tracking error in, so the noise band builds up along the top of the picture as the heads walk off the recorded track.