I really am surprised the group you were shooting got worse. I would have suspected they would have been really good. With a clean dry barrel you are shooting as close to the same, shot after shot. I use the same bore swab solution and have never had any problems. I have noticed sometimes the sabots on hot days are harder to load. All I do after pouring the powder down the barrel is to wet the outside of the sabot with spit from my mouth and it seems to seat just fine. That little bit of water is gone long before it reaches the powder charge.

I personally suspect it was the warm temperatures. I find my black powder rifles alway shoot better in cool to cold weather then in hot weather. If your barrel was hot to the touch, I suspect that the plastic of the sabot was trying to grip the rifling on the way down.

Let the barrel cool more between shots. Also do a longer swab routine. There is nothing that says you can not use two or three wetpatches down the barrel. And do not forget the couple of dry patches following the alcohol/windex patch. Also try the spit trick next time. If this happens again, put a patch in your mouth and swab with spit. See if that makes a difference in the loading. Hot weather is the worst time to shoot ... especially sabots. Summer time I usually shoot round ball or conicals for that reason.