That's an awfully thin patch. I bet that goes down a clean bore mighty easy? It may not even be filling the grooves completely. You have a RB .005" under bore diameter and a .007" patch to take up the rest of the room, which includes needing to compress into the grooves tightly enough to seal. After shooting that first shot you load the next without swabbing. A lot of fouling is left stuck to the bore and the .007" patch doesn't scrap much of it back off. It loads hard so you may be deforming the RB as well. Your next shot with the fouling in the bore results in a much tighter fit, so pressure and velocity increase some. You get quite a bit higher POI due to this.
That is my belief in what is causing your significant clean bore and fouled bore variation.
I personally would go to a thicker .015" patch. Ditch the prelubed store bought patches. Take some of your Ballistol and mix one part Ballistol to 6 parts water. Shake well. Dip unlubed patches into it and then set them on wax paper to let the water evaporate off and only leave the Ballistol behind. You can experiment with different ratios between 4:1 and 8:1. This is a Dutch Schultz style of lubing patches. Very consistent method. Patches curl up when they dry, only complaint I have about it. If you have screen material it'd be better to put the patches between two of them, perhaps wouldn't curl near as much. Swab between shots when developing an accurate load. You can later test how accuracy and ease of loading is without swabbing. I like the benefits of swabbing so much I simply do it all the time, at the range or hunting. Many worry about a fast follow up shot when hunting. I'm 48 years old and have hunted every single year since I was 12. I've needed a fast follow up shot exactly once to finish off an animal I hit poorly. I either hit them and they run off, or I completely miss and they run off. I wait to track after shooting one anyway, so an extra minute to swab the bore is nothing in the grand scheme of things. From experimenting I also know that I can load a 2nd shot without swabbing if I really need to and accuracy is close enough. It goes out the window with a 3rd shot though.
If you don't want to change things much right now, another suggestion. For your clean bore shot variation you could try a thicker patch with the first load. Many load the first clean bore shot with a thicker patch and then go to a bit thinner patch after the bore is fouled. Helps lessen the deviation between them. You could try doubling up your .007" patches for that first clean bore shot and see what the results are.
