Yep, definitely sounds like there should be a sanity check for slashes (both forward and backward)…
Sadly, you can’t rename the snapshot directory, as the ID is saved and referenced in the encrypted snapshot file.
To fix your backup, and to avoid transferring it all again, initialise a new repository ID - maybe use a dash instead of the slash.
Before you do that, you may want to manually remove (or rename) the hidden
.duplicacy at the root of your repository, so it’s able to create the new ID for the default storage.
When you run the new backup, it’ll seem like it’s doing it all over again, but should skip most chunks. You’ll end up with a new snapshot folder on the storage and you can manually delete
snapshots/Keith/Pictures and run a cleanup with