Hello. This is a total shot in the dark, but as someone who enjoys flipping their spacebar on their keyboards I find that the regular orientation of the buckling spring spacebar keys to be a bit uncomfortable. I have made an attempt in the past to model and 3D print a compatible spacebar that attempts to flip the standard orientation of the spacebar while maintaining the stem and stabilizer orientation, however I havent found much success (unexplainable issues with the keycap remaining stuck in the depressed state). You probably have more pressing projects to worry about but on the off chance that this may interest you, it would be wonderful if it were possible to release a spacebar mold that is either flipped or has a softer bottom edge so pressing with the thumb is less intense. It’s really the only thing keeping me from using my keyboard more often. I look forward to purchasing a B62 when the time comes for that to release! Thanks.
My recommendation is to borrow a Model M bottom key stem and design your 3d printed spacebar to accept this stem. The tolerances of 3d printing probably are causing your issue with testing a 3d printed spacebar. Molds often cost tens of thousands of dollars. Please keep me updated if you proceed with this project as others might have some interest in it.