Just did my first restore today and everything worked fine. Sadly it was same state as before
In detail: several weeks ago the device started to behave strange. No Version information (just a lot of ?), backup no more to internal memory only to sd card and now it won't open my IMAP inbox anymore (all other folder work well, only inbox doesn't react). so I thought it might be a problem with filesystem and some broken anything. But at least backup and restore didn't do anything better. So now I'm gonna prepare for a full reflash. Damn, that's gonna be a lot of work to get it personalized again