Custom checkbox stays enabled in create screen when clicking on 'Create another'

We have coded a custom checkbox that is selectable in the create screen (when creating a ticket). When creating test cases from the Requirements page, if the ‘Create another’ option is selected, the next test case in the create screen has the custom checkbox enabled and unselectable (it becomes greyed out and you can’t click on it).

It seems to happen only when creating test cases from the Requirements page.