CMJ Integrity Check reports "Issue type 'Test' has duplicates."

Symptoms:

During an integrity check or when creating a snapshot CMJ reports an error: 'Issue type 'Test' has duplicates'.

Cause:

There is more then one Issue type with the same name ('Test'). This is not allowed through the Jira GUI. The duplicate issue type was introduced through the database (manually, with a script or 3rd party app).

E.g. when both Zephyr and xRay are installed, they both create a 'Test' issue type.