It's a technical problem with one particular camera during taping, which is why it only appears in those shots.
If it was a problem with the master it would run through several shot changes.
This visual anomaly was present during original taping and is present on all editions of the episode, from VHS to DVD. The only way to correct it would be to artificially zoom-in the shot during the original mastering, but that would crop the original shot on three sides, and be another example of fixing famous goofs...and we don't want that.