When I installed mine, the spring was not positioned right making some gears harder than others, maybe this is your problem also? Try changing the orientation of the spring, I have also heard of others not using the centering spring at all, havent tried it though. Anyone that has, please post opinions.
Also the B&M is much more "notchy" than stock in my experience so that might be it also, that you just have to get used to. Then again, I have never had it pop out of gear.