I dunno...
This sounds suspiciously like a mode page problem.
I wonder if perhaps the wrong mode page was downloaded to the drive...
i.e., the drive is 36G, but it has a mode page for an 18G drive.

Seagate makes depop versions of drives... that is, same drive with
fewer platters/heads. Everything else is the same, including firmware
(generally speaking). Only difference is in the mode page settings (and
the physicality of the drive, of course).

Downloading a proper mode page would (if this is the case) correct the
problem. But I wouldn't mess with a boot image. If it's working and
you like it, don't worry about it.