Sadly this is what nomally happens at dance comps, if a judge doesn't like what you are doing just at that moment,for whatever reason, you probably wouldn't get their mark to be recalled into the next round.
I would have liked all couples on the floor for the duration of the song, it would have been a good test of stamina and give the viewers as well as the judges ample time to compare couples.

I thought Susannah and Kevin from Grimsby seemed to be doing jolly well.

I thought Sophie and Brendan would be going out first as she again looked listless and floppy, even at the start of the dance

I wouldn't say the swingythong was fixed, it's just one string on a whole fiddle of things that can be used to manipulate outcomes on SCD.

With regards to Susanna and KFG, I wasn't quick enough to spot them before they went out

Natalie has actually been undermarked for a couple of weeks now, I think in an attempt to make it seem as though the other girls are catching up to her. In fact, Abby is really the only one to almost do so, although Susannah's improvement has been amazing. Sophie has gone downhill from that Charleston, but is still being overmarked by the judges, who are hoping she'll deliver. She won't, it's too late in the day and she still doesn't have basic skills like a sense of her own core/centre, nor can she seem to spot when doing even a simple turn, let alone multiple rotations.

Natalie has dance training, as have many former celebs on the show. It always amazes me how some viewers seem to think it possible to have a level playing field in this respect.