Massey 88 Loader Problems

I purchased a Massey 88 with a Doall loader on it. After using it for a 15 to 30 minutes it would stop lifting. When it does lift, even without load it pulses. You can feel it in the hose and the front end bounces. There have been a couple times where it would seem to be working great and then just goes back to the same old problems.

So far we have changed from the transmission fluid that was in it to an all purpose 100 hyd fluid. We took the pump out and apart and cleaned the screens (everything looked good). We tested the pressure coming out of the controls 20,000 psi right away and 15,000 psi after it was worked beyond what it seems capable. We changed out the controls too. We cleaned the filter and added a transmission cleaning product to try to break down anything in the valves etc.

The tractor is otherwise in great shape and my father-in-law wants to get past this so he can start painting it up and getting it looking good.