Hello Farzad,
If I understand correctly, then you face this problem when you are switching from Parametric to Simulate. isn't it?
May be you can try this:
This issue occurs when the model is over constrained or some assembly references are lost (see video below)
- Highlight the part for which the connection is defined
- Right click and select > Info > Parent Child from the popup menu
- Suppress all children of this component and take the model into Pro/MECHANISM
- No error should be reported now.
- Start resuming the children one by one until the error appears again
- The child component causing the problem should be redefined so that all references belong to only one component
and refer this video
And if this does not help, then will you elaborate more about the model?
Best regards,
Jignesh