The Vickers Viscount was a kind aircraft to pilots. I cannot explain the technical issues but even a late flare and what should have been a firm landing often turned out to be a greaser.
I know of one airline that has a Boeing 737 Classic simulator where it is impossible to do a hard landing. ALL landings are soft when it was clear the landing should have been a real bummer. The technicians fiddled the computer to do soft touch downs in order to minimise maintenance on the instruments which can suffer from heavy impact touch downs.