I got the block number to use on reassign from the output of an SCSI error
message, which was "Check condition on CDB" and printed "CANNOT READ BLK
X" on the Info Field. Reassigning never fixes this for NetBSD, even though
the scsi reassign command is successful.

> If you were feeding the block numbers from fsck into "scsictl
> reassign", that may be the reason it didn't work.  You need to get the
> physical block number.  If you have the SCSIVERBOSE option in your
> kernel, the error message will be displayed in a quasi-readable
> format.  The physical sector number, if I remember correctly, will be
> in the "Info Field" of the error sense code dump.
>