I dont know anything about that clamp but the company that builds that clamp has distributors all over the world l did find one that might be able to help you that is not that far in turkey maybe they can get you or direct you were to get a hydraulics digram to check it out there number is+902164704660 it is called Fama forklift kaup turkey hope I was of help

Thanks for comment.
It's kaup 2T013

Thanks for your response,
It's kaup 2T013, if I had it's hydraulic circuit I could figure out where is the problem, it's cylinder doesn't have check valve on pressure port.
There is a block on clamp I must know what's going on inside it.
I should to add, it happens randomly not always. And it makes it scary.
Where should I find the hydraulic diagram?

I dont know what clamp this is but most manufacturers install lock valves inside the cylinders just incase the packing or the valve is leaking internally after the clamp is shut closed the valves hold the cylinders so not to drop the rolls and kill someone l know if it is cascade clamp the valve are set at around 900 psi to open on the back stroke it is possible that the valves in one is going bad just thinking but you will have to take pressure test to see were the problem is

If it's a Cascade clamp, they have service manuals online.
cascorp dot com/us/en/serviceliterature