What did you change that eliminated the problem? I assume that running a 90%+ alcohol patch down the barrel would remove anything left in the barrel from cleaning, but I've also always read to finish up with an oil patch down the barrel to avoid oxidation.
Ok, this is highly controversial, so I say up front that I'm not making any pronouncements, only stating my experience.
For a very long time I used Shooter's Choice only with a bronze brush and was completely satisfied. I never had clean barrel flyers or a need to foul the barrel for several shots before it held consistent point of impact. A few years ago, I had to change to an odorless solvent because the odor was having ill effects on a family member.
After reviewing the various solvents, I decided on Bore Tech C4 w/ bronze brush and Cu+2 for copper cleaning. I began getting clean barrel consistent flyers. Even worse, it took several shots to obtain a consistent point of impact. I couldn't figure out what was wrong because I was doing everything the "experts" claim is correct.
With the aid of a fellow shooter and some research I stumbled on a few proponents of the concept of maintaining copper equilibrium. At first I didn't believe any of it but decided to give it a try. I stop using Cu+2 and just used C4 with a bronze brush which does an outstanding job of removing carbon. Bingo, everything settle down and for the past few years, using this method everything has returned to normal.
Bottom line, the only conclusion I can think of is that I was removing too much copper. I suspect that C4 acts similar to Shooter's Choice relative to copper removal, it removes some but not much.
For technical explanation go to gunblue490's videos and watch the one of Cleaning Solvents and How to Clean Your Barrel Professionally. There are others too, but I would start with this one if you're interested then draw your own conclusions.