QNX 4, cat /dev/hd0 | gzip -c -best | vol -w /dev/fd0, Err

I have a target computer with 16M Solid State Disk (SSD). The SSD is
represented by /dev/hd0
In order to dump contents of the SSD to floppies I use this command:

cat /dev/hd0 | gzip -c -best | vol -w /dev/fd0

and to restore

vol –r /dev/fd0 | gzip –cd | cat > /dev/fd0

Usually (say nine times out of ten) all works fine. However, from time to
time I get messages like the following:

Vol: CRC mismatch in volume 6
gzip: stdin: invalid compressed data – crc error

and volume 6 will be bad indeed.
The problem is not caused by faulty floppy disks or floppy disk drive. I
would appreciate your comments.