Comment # 1 on bug 1214219 from Stanislav Brabec

The problem is not in smartmontools. It is a problem of the disk firmware. And
only the manufacturer knows, whether it is critical or not.

Perc_Avail_Resrvd_Space reaching 0 means, that the drive went completely out of
spare blocks, and in the next occurrence of a weak sector, it will fail to
relocate the failing area.

Anyway, smartmontools has a database that makes possible to ignore confirmed
firmware bugs.

We do not release the database updates as an online update, unless there is a
business case for that. Users of community products can update this database
directly from the upstream by the command called as root:

update-smart-drivedb

Once the upstream releases the database, just run the command, and you should
get your error hidden.