Hi, the only way is to change it at database level. You can even try to change, into the database, the newsletter status from sent to paused, change it from the editor and ten set it to sent once again.
I had to go in and duplicate the newsletter, make the corrections, and then you can send out the “new” version. Then just delete the old one!
I also had to do this to resend the same one a second time.
Hope this helps.