Your hydraulic system works on a priority system. The remote valve for the loader get the pressure first, then the 3 ph.
My point is that one of the spools of the valve MAY have malfunctioned or is out of position. The hydraulic pressure will be diverted before it gets to the 3 PH.
I bumped one of the levers on my valve this spring and the 3 PH suddenly was VERY SLOW to raise and I had to rev the engine to get it to even move.
After I scratched my head a few times, the light bulb came on and I wiggled the levers and presto, it was back to normal.
This is something to check before you go tearing it apart.
May not be your problem, but may help to diagnose it too.