i try using backitup for our backup, but mostly if the disk is full, there occurs an error. In German “Abbruch durch Benutzer” - I think in original it’s “Canceled by user” or s.th. like that

I’m using the NEC ND-1300 and TDK DVD+RW.
If i manually erase the disk, the backup works fine.
I know, there is an option to erase the disk automatically an wait for a couple of time, but it does only sometimes work.

where is the problem?