I went to the Kimber web site and checked what their upper conversions look like. Not the best photo's ( <-- Hint hint ). As best I can see there's only one hole at the base of the barrel for the slide release.
Again, without pics I'm kinda guessing but if installing the slide release causes the barrel to drop down to the point that it's jamming the gun then I'd have to say it a defect. It has to be drilled out of alignment or something similar.
Best bet is to try this. Install the slide, barrel, and bushing ( no recoil spring or plug ) and see what happens. I'm highly doubtful that a burr would cause that kind of failure but check with a light and magnifying glass to see if the slide stop hole has been cleanly cut.
Also check the 22 barrel's fit in the frame all by itself and with the slide stop pin installed ( but no slide or other stuff) It's barely possible that the barrel is oversize to the lower cutout.
gl