Drive: HP Ultrium 448 SCSI
OS: FreeBSD 4.11
Amanda: Version 2.3.0
FreeBSD 4.11 is also pretty old, but I wouldn't expect any trouble from it.
I would use dd and copy all the data from the tape back to holding disk.
As a general rule I try to read the tape exactly once, and in streaming
mode, when doing restores, since you never know how many times before it
breaks.
That will remove amanda from the equation of restores.
I have a quantum LTO2 drive, on NetBSD 4.0-stable and amanda 2.4.x, and
haven't had any trouble with it. But I'm not 100% sure I would have
noticed your problem if I have it.