Rotary grabber losing grip on paper rolls

[my.father]

Got an issue with the rotary grabber on one of our lift trucks that's been giving me a headache, every now and then, after it clamps onto a paper roll, it suddenly loses grip and drops it. I've already checked the clamp cylinders and they look good enough cos there has no visible leaks, and they hold pressure fine when tested on their own. Unfortunately, I don't have a hydraulic diagram for this setup, so I'm flying a bit blind here
TIA

 

[Donkeys8561]

That doesn't sound good. Try inspecting the check valves or any internal lock valves. Some clamps rely on those to hold pressure after gripping. Also, if there's a control block on the clamp, that could be the issue.

 

[Azusa]

If it's bleeding off under load, the grip will fail without obvious leaks. I'd check the hydraulic flow and pressure while operating, and inspect the hoses for internal collapse