Backup to Dropbox = 2 errors (not enough space, file size missmatch)

Hello,

I am using BackWPUp in connection with dropbox for several sites without problems. But since a few weeks I got for one site the following errors:

WARNUNG: You do not have enough space in your Dropbox.
FEHLER: Gr??e der lokalen und der hochgeladenen Datei ist nicht identisch.

(The second means that the sizes of the local and the uploaded file aren’t the same.)

I got quite 1 TB free space in my dropbox. And all the other sites working fine. What means that error, what can I do to try solving it?

Thank you for any help

Realbilly ??