+1, I have been there and done that.

OP, I had the same exact issues with Blitz when I installed a Tekin system in it. Couldn't finish more than a few laps in a race because the pinion would never hold on.

I was using L-wrenches since 2002. They always worked well enough on nitro for me so I didn't think anything else of it. As it turns out, quality hex tools are finished to much better tolerances that you need in order to get just the right amount of torque on the pinion. Another racer saw my issue, lended me his hex tool, and the problem went away.

..I bought a whole set of hex tools the very next day.

Mine aren't a very high quality, but they get the job done. I bought a set of Dynamite tools. I'm not sure how I got by without this type of tool before. I hardly ever touch L-wrenches anymore.