It's been my experience that at conteast a model will get moved for various reasons, placed in wrong catagory, moved to make room for another entry, moved so the judges can get a look at the other side, and so on.
I've known many guys that covered defects over with extra gear, containers, or tarps to cover an area they noticed that was too much trouble to fix or found too late.
I've judged in the past and have seen some pull out T.O. and start checking details and paint jobs for the correct patterns and comparing paint chips against the model. In both cases there's going to be variations, fading paint and no aircraft will follow exactly the drawings for multi-color patterns. They may be close, but not exact. For example, with the C-130s in the 70s there were a lot of units that altered the pattern on their tail to show what state they were based in.
I had a judge assigned to me once that as we approached the table we were asssigned, he started to make comments about how many times he had seen a certain model in contests. I immediately called the judge supervisor over and informed him of the comments which would make him predjudeced against the entry and then excused myself from the judging on the grounds that the model he just put down was a first time entry, with over 6 monthe work on the flight deck alone and that I was the builder and not supposed to be in this catagory.