Long ago in a 3.x version there was a (client) bug that went something
like...
 there were 4 bytes of control info, the last byte indicated if a file was
compresses, routines always assumed the 4 bytes would be together within an
inbound record... when the randomness of data actually split the 4 byte
field across two different inbound records, garbage was loaded into the last
1, 2, or 3 bytes of the control field giving a situation such as you are
seeing.
In our case, the data was OK but we had to get a client fix before we could
get some files back.
Maybe this bug has raised its ugly little head again ! ?

just FYI
        Dwight