Another way the filter can get crushed, destroyed, mangled is moisture in the hydraulic fluid. If the tractor sits outside and it freezes the water molecules get trap in the filter before the hydraulic fluid has warmed up. The water molecules, ice crystals, basically plug the filter and the hydraulic system pressure crushes the filter until some of the hydraulic fluid can pass thru. I have seen this numerous times. Now if you live in Florida the bets off. LOL