I am trying to minimize stress in a screw pullout test by optimizing the geometry (pitch, thread profile, etc.) of a bolt-nut assembly where the threads of the nut are made (using the component operation "Cut Out") by the bolt. The FEA runs fine but the optimization study gives the initial values as the optimal values every time for each geometrical characteristic being optimized.

I DO think the nut is being updated when changes are made to the bolt for these reasons:
when the cut out was performed, if I select "no" for "Support associative placement for the feature," I get warnings of cracks between the nut and the bolt during FEA;
if I select "yes" for "Support associative placement for the feature," I DON'T get warnings of cracks between the nut and the bolt during FEA. (So now I always click "yes")  
Both result in the initial values as the optimum.  The values tried by ProMechanica don't vary much from the initial values (not close to the limits set).

Please help