Hi Steve,
In the past, issues such as this have been found to have been caused by a connection issue between the sites and Google Drive.
UpdraftPlus attempts to access the directory in Drive, fails to find the existing folder because of a connection issue, so creates a new folder with the same name. It later cannot find the old backups as they are in a different folder.
If this appears to have occurred recently, please could you send us the backup log?
The contents will be too long to post here directly, but you can use an online service such as Google Drive or Pastebin, and post the link here.
I’m afraid that you will need to manually delete any older backups left on the drive in the wrong folder.
Best Wishes,
David N