I've had several experiences lately where DVDs burned with brasero that pass the post-burn checksum test actually have I/O errors when read back with dd.  I wouldn't expect this if brasero were actually reading the entire disk to create the checksum, but it's happening too often to be coincidence, so maybe it just samples ?

No errors with k3b, which seems to be reading the entire disk and comparing to the original.

I'm not sure why brasero bothers with the checksum business if it's going to read the entire burned disk; it might as well just do the compare and save the cost of checksumming the ISO image at the start.