something comes from the side and messes up your data in a different way than you've foreseen.

This happened to me years ago. Naïvely thinking SnapRAID protected me against the likelihood of a drive failure. I wasn't prepared for two drives failing simultaneously due to a power supply catastrophically failing (smoke, sparks) and frying the drives as it died.

It was an expensive lesson: I had to send one drive off for data recovery, and after I got it back I used SnapRAID to restore the remaining drive. Independent backups (and multiple parity drives) is the way.