Scott
What your describe is extremely unusual. In fact, I’ve never seen it happen. Try this, take the power valve out. Remove the blade. Use a bit of red Lock-Tite and re-assemble. Use a 10mm wrench to hold it to seat the stud and blade. It should not come out. It is possible the threads in the diaphragm are stripped and not keeping the stud seated.
16 to 20 turns out is best for the adjustment.