Issue: This warning may occur when you copy an element from the main model to a design option. In this case, the element exists in the main model and in the design option. As a result, these 2 elements overlap.
Solution: To resolve the issue, delete the element from the main model or from the design option.
If you tried to move an element from the main model to a design option, cut the element from the model (instead of copying the element), or use the Add to Set tool. See Moving Elements from One Design Option to Another or Moving Elements from the Main Model to a Design Option Set.