zero point

i been working on one of the harmonicas that am trying to restore. and i got all the over blows working on holes 1,4,5,6. the zero point on the draw reed on hole 5 wont set. i put the draw plate in a vice and tried setting the reed. The 5th hole draw reed zero point would not set. Then I tried setting the individual reed with richard sleighs reed shaping tool using the knife edge. And it still wont set. and it causing my over blow on hole 5 sound week and harder to play. Any suggestions.