Doctors on UK Gold today

I am watching Doctors on UK Gold at the moment and I noticed half-way through a scene for about a minute, the film effect vanished, then came back. How is it that it slipped though without being noticed at any stage? Surely with the amount to previewing and technical reviews that are supposed to happen, shouldn't something like this be picked up on before a show goes to air?

Could have been an edit made for UK Gold ? Usually the flicker effect is added after editing, but before captions are added (so that the captions aren't flickered) - maybe they went back to the rushes or an earlier edit for a sequence to drop into a master, or maybe the original had a very late edit?

One thing I've noticed is that Doctors is a technically dreadful programme. Some scenes look so bleached out, and very low res, as if they were filmed with a cheap DV cam and simply de-interlaced to achieve the film effect.