Has this issue been repaired? If not , I repaired a KB&B stem by removing the metal screw in tenon from the bit entirely,screwing into the
shank and epoxying the bit back onto the tenon. you would need to drill out the threads in the bit just enough to allow you to push the bit
back on. If the tenon piece wont unscrew from the bit try warming it in boiling water to pull it out.