Dunno if this will help or not, but ....
https://docs.moodle.org/400/en/Content_bank
Says:
Restoring a course with a content bank
When restoring a course, the content bank contents are also restored to the new course. Please keep in mind that the user who restores the course will be the owner of the content bank contents in the new course, and this will affect who can edit or delete the contents based on the Delete any content from the content bank and Manage any content from the content bank capabilities.
https://docs.moodle.org/400/en/Capabilities/moodle/contentbank:manageanycontent
On your second screen shot it showed a 'more info about this error' link. Where did that go?
'SoS', Ken