Here's my 2 pennies:
You mention "jerking" the trigger and that you used the good ol' "cap and ball" drill (dummy rounds) to identify it.
By jerking do you mean pulling the trigger too quickly/slapping the trigger?
Or do you mean the "flinch" or "pushing the shot" or whatever you call it when your sights dip down because of anticipation of the shot?
If you notice the sights are moving as the hammer goes "click" on a dummy round in anticipation, it's a flinch - or whatever more PC word you choose to label it. That means part of the fix is mental. How can you convince yourself that the explosion going off in front of you isn't worth flinching/bracing for? You can pre-occupy your mind by concentrating on the front sight. Try to see every detail of the front dot - if there were tiny words written across it you'd want to be able to read it. Keep your focus there as you gradually increase the pressure of your trigger finger - but don't concentrate on the trigger finger, just the front sight. And also try to keep your eyes focused on your sight during recoil and until they settle back down again, aimed and ready for your next shot. I like 10-96's description of you as a platform and I think of that word sometimes when I mentally picture the process. You're presenting a straight line between your eyes, the front sight/channel, and the target and you hold it there like a waiter with a silver platter balanced on his arm. You become a machine and the only thing that moves is the trigger finger. Dry fire practice has helped me tremendously with my flinch (but you don't want to dry fire a .22 without snap caps, more likely to damage gun than centerfire).
If it's simply jerking the trigger (shot groups would be low and to the left) then it would help to slow that trigger pull down and look up "compressed surprise break Jeff Cooper" on youtube. He explained it better than I can in that video.
All shooters have to practice to work against both (and other habits) since they can creep back in from time to time.
Just a theory, but I agree in that Single Action mode, it's more tempting for the body/mind to want to control the trigger break since the trigger travels a shorter distance. The body thinks, "I'm going to prepare for the blast by making it happen *now* [pulls trigger too quickly] and I'll brace for that blast/recoil by leaning forward and pushing the gun down right *now*]. In Double Action your trigger finger is already exerting force throughout the long travel and since the trigger pull is so long it's less tempting to force the trigger to break as it would be more obvious.
- as you can see, sometimes I feel like my body has a mind of it's own
and it's not me
Happy shooting, wish I had a 22 pistol, I would shoot a WHOLE lot more.