Comment 7 for bug 877631

Hello! I've figured out why this is happening, I think. Is the following scenario likely?

1) You started your first ever backup
2) You chose to encrypt it with a password
3) Your backup got interrupted
4) You later backed up again, resuming the backup
5) You were prompted for your encryption password again, but mistyped it (and DD accepted it without question)
6) Later, you got this error

I can reproduce the bug with those steps.

As for your other questions, more advanced include/exclude support is bug 374274. And yes, Deja Dup is making incremental updates. But every now and then (ever few months by default), it will make a fresh full backup.