[old_tv_nut]

The menu text is generated by internally syncing the character generator to the sweeps, so even if the sweep is not synced to incoming video, the characters are still stable.

The external image jumping is some kind of sync problem, either simple sync separation or improperly locking a horizontal-to-vertical countdown to the incoming signal.

So basically yes, this means the horizontal and vertical sweep circuits are OK, but something in the preceding circuits is wrong.