Scoop on the fly....Common to see driver`s pick up a load without stopping. I have seen many tilt cylinders leak at the welds.
Other than that, age, high hours and cold or hot environments are main cause. Many cracked cyls I replaced had bent mounting brackets or broken bolts, obvious impact damage. The reach cyls are affected the same way, as are the main lift cyls on many trucks.
Yes a few are bad welds, but most are excess pressure build up.
A Hydraulic rebuilder showed me how much these cylinders `Bulge`
when pressures hit the roof. These cyls balloon and flex more than we realize. The welds are the spots where there is little flexibility, so leaks will appear there first. I have fixed main cyls for bottom end cap leaks. Spot welds are temporary. A new bottom cap will fix it. The cracks appear with high hour trucks that go `dead head`each time the driver runs the lift to the top and forces it. You will see some blocks leak at welds where the cyl has a flow control valve in the block. That forces pressure too high on collapse as the restriction is biggest at the block. Only the right main cyl and left main free lift cyl cracks on a Raymond 7400 as they both have flow control valves.
We have successfully re-welded these block back on, but spot welding rarely works. The factory approves spot welding.