Macrovision is a copy protection originally introduced in 1979 at the beginning of the VCR age. Essentially it prohibits users from a 1:1 copy of a protected video. Largely apparent as contrast shifts in your copied tape, I believe this may be an early form of the macrovision copy protection which manifests itself as obnoxious lines in your output signal.

Of course I may well be wrong, but I do seem to remember watching a copied tape of Jaws back in '79 or '80 which shared this same feature.