Based on what you have posted, it is not obvious that it is TCP
at fault.

I have seen cases where files transferred with wget/ftp were corrupted.
I have seen cases where files transferred with uucp were corrupted.
I have seen cases of "guarenteed reliable" networks running on
very highly reliable hardware (redundant, running off battery,
monitors and alarms on everything you can think of, several 9s
uptime requirement, failure could indirectly result in death,
test cases written for every line of code) drop packets.  I
have read the same sector from a disk multiple times and gotten
different data each time.  (Fsck should check for this problem
before modifying disk contents, otherwise things just get worse.)

Pretty much any piece of hardware the data goes through could
cause a problem, either through a broken piece of hardware or
a buggy design.  Any Intel CPUs in the path?  Any PATA disks
involved?  SATA (and I assume SCSI) check both the data and the
command, but PATA only checks one.  Anything overheating?

> the restore of it to a test system would often be corrupt

If it is happening "often", it is worth hunting down and fixing.