*EDIT* - this is actually a generic issue. Any project I try to delete in this instance is giving a 500 error.
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While merging instances and moving projects from one Jira to another, I ran into a problem. Project Configurator was creating "temporary projects" - I wanted to delete the temporary projects but when I tried I got a 500 error. I need to remove these so I can import the real versions of these temp projects, but all attempts to do either are failing.