You can't delete an issue from a board. A board is just a "view" into one or more project's issues. The issue is really deleted from a Project. The Project is the actual bucket of issues.
So the TB board and Copy of TB board are probably looking at the same set of data.
If you delete an issue from a project, it will be removed from every board that points to that project as well.
To see this feature in action check out our recent dependencies demo here: https://www.youtube.com/watch?v=eQu5VsUqyZA Keeping on top of your dependencies is a key part of ensuring project success....
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