error with dropbox sinc

since 3 days, all of my backups give me the same error:

Dropbox-API: (507) Dropbox was unable to complete this action because of a storage quota limit. https://content.dropboxapi.com/1/commit_chunked_upload/sandbox/xxx.tar.gzArray

But my storage there is 1tb, and actually there is not more than 5gb up there.

https://wordpress.org/plugins/backwpup/