It’s the opposite, they’re not ductile. My guess is that by pulling the nuclei away from each other, the atomic orbitals don’t overlap as well anymore, destroying the covalent bond.
Had the same problem. @Rubén, it’s on the bilbao website https://www.cryst.ehu.es/cryst/get_wp.html. You enter the space group and underneath that box is a button ‘ITA settings’. You press that, and it gives you the correct result.