At first I thought my internal BD-R burner was at fault, but this happens with a USB 3 burner, too. The disks burn, but usually fail verify. However, if I do this, it doesn't report any error:

cmp /dev/sr1 /home/user/tmp/Alice.iso
And the disks seem to have valid data, as far as I can tell. Single layer Bluray disks verify, though. I couldn't find any current threads on this subject...
Is this a known problem with K3B, or cdrecord? I was going to try burning with growisofs, but that was burning at only 2.4x, I didn't want to wait all night for it to finish.