When backing up/cloning a whole drive using the popular app SuperDuper! to a disk image, sparsebundle, Avast mistankingly will put in the Chest some of the sparsebundle bands, this action effectively damages the backup.
I had to boot into safe boot just to make sure there were no interferences by Avast, I also didn't turn the file shield off because the clone is suppose to work as the original (I.e. It would be cloned with file shield off).
I had noticed this before but because last time I clone the drive was months ago I had forgotten about this terrible behaviour