What is this visual artifact called and why does it happen?

[RoboMWM]

I've tried to lookup what this might be; nearly half the screen gets snow for 2 frames and sometimes the audio also briefly changes pitch/speed.

I've narrowed it down to my Panasonic PV-4664 VCR causing the issue as it happens in different times when playing the same tape, and does not occur with the same tapes in other VCRs. It happens at random intervals, from seconds to 8 minutes will pass before it happens again.


[Attachment 91459 - Click to enlarge]

[Attachment 91460 - Click to enlarge]

What is this called and what in the VCR might be causing it?

[Selur]

my guess:

Dropout

Brief signal loss caused by a tape head clog, defect in the tape, debris, or other feature that causes an increase in the head-to-tape spacing. A dropout can also be caused by missing magnetic material. A video dropout generally appears as a white spot or streak on the video monitor. When several video dropouts occur per frame, the TV monitor will appear snowy. The frequent appearance of dropouts on playback is an indication that the tape or recorder is contaminated with debris and/or that the tape binder is deteriorating.

source: https://cool.culturalheritage.org/byorg/bavc/bavcterm.html
but others can probably comment on this more,...

[Sharc]

Dropout, TBC error/glitch or tracking error perhaps....
Maybe you can check against the examples provided here:
https://www.avartifactatlas.com/