That’s good data. Hopefully one of the SUAC has an update on whether the previous bug for deleting duplicate sub-units has been resolved or is still outstanding. You should still be able to add scouts to the “correct” den from classic Scoutbook (I think) by using the Invite Members button in the den you’re adding them to.
Looks like the same issue as here:
https://discussions.scouting.org/t/duplicate-lion-den/506423
ETA: It occurred to me to ask whether there are any registered scouters assigned to the den as a Den Leader and/or Den Administrator?
