https://www.bbc.com/news/uk-politics-16746389
It's clear your example that they (Swedish MEPs) were all agreed to vote in this direction, since they each press their own button. It's most likely that they didn't understand the significance of the vote and thought better of it afterwards.
It's their one job, to vote.
> A spokesman for Mr Stunell, MP for Hazel Grove, said he had voted against the Labour amendment "as he was supposed to" and had gone to get a drink of water for a fellow minister when he found that lobby doors had been "locked".
> "He was temporarily on the wrong side but sanity prevailed and they let him out," he said.
A funny story, but not a legally significant outcome.
Here, it's suggested that MPs sometimes vote both ways to cancel their own mistake out, although they normally claim that they are taking some nuanced view: https://www.publicwhip.org.uk/boths.php
Not to mention that UK MPs can't vote if they have to be absent for any reason - for example if they have child-care duties.
Your original point was that the UK Commons' system of slow voting is foolproof: it isn't.