While I am thinking that the box is probably the problem, I am fairly confident that you can't test it by disconnecting the ram mechanically without disconnecting it hydraulically as well. If I remember correctly, it has to build pressure in the ram lines to work correctly. Otherwise it doesn't give the proper pressure in the box control valves. The ram will become a pressure leak until it hits the end of stroke. I believe that is what I found out several years ago when testing one.
I would cap the ports on the box and see if things change, it may still not be how you want it, but I think that it should react more normally, even if it still has a hesitation.