How can we uncheck the "Skip creating a new assignment and leave the existing assignment as is" box?

Summary:

Skip creating a new assignment and leave the existing assignment as is. We need to assign something one off but there is a future dated assignment . The "Skip creating a new assignment and leave the existing assignment as is" is checked and cannot be unchecked even on the Catalog Defaults page. How can we uncheck this box.

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23D

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