something like that could be a hardware malfunction. Did you try it on different machines ? On my workstation at home, there's a fault either in the CPU or RAM,

something like that could be a hardware malfunction. Did you try it on different machines ? On my workstation at home, there's a fault either in the CPU or RAM, that I only discovered when trying to make large backup archives. I made 40gb archives and ran md5sum to confirm integrity and occasionally the sum would differ between 2 consecutive operations. So either the ram or CPU/chipset has a bug during heavy IO operations. But I never fixed it because 99% of the time I never notice it.