Yes, that can indeed cause a partial "burn-in" on a loop tape.
EDIT: I work with computers, and I know that a hard-drive can suffer from prior corruption if that newly recorded area is not "cleaned" 3 or even 7 times prior.
A "residual effect" due to the way magnetic coatings tend to slightly hold on to prior recordings.
Some CCTV recording devices use loop tapes(VCR type tapes, but looped) for recording, whereas others use a hard drive, which is often re-recorded(depending on capacity)
There is no technical advantage to looping(in fact rather it's a hinderance), just cost savings.
Either way, with tapes or hard drives, true "scrubbing" takes time, and the more expensive systems use a dual recording media(one is "scrubbed" while the other one already "scrubbed" automatically takes over the recording.
I don't know, but I somewhat doubt that the pub in question had the more expensive system.
Edited by pallidin, 20 February 2014 - 06:06 PM.