See what you think of this idea, suggest any changes, prepare as needed, try it, and tell everyone if it works. Although this backup doesn’t sound too important, you could try to preserve it in case a next-idea is needed. Maybe it could even be used someday to try new Duplicati code to fix this so such manual work isn’t needed.
EDIT: or is it too late, i.e. has the database with “Unexpected difference in fileset” moved to a different error?
Thanks!