When you recognize that your optimization result is growing in an inappropriate way, than your optimization went wrong
The main reason is that the nondesign spaces on which the structural loads are applied tear off and lose the connection
This results in iterations where 0 MPa stress occur (see picture below)
In the following iterations the model is growing again due to zero stress
If its connect again with the Nondesign space a stress will appear again
...
Solution:
The occuring stress doesn’t fit to the optimization goal
Lower the optimization goal
Increase the applied structural loads
Increase the Complexity for a higher resolution