Oliver 1956 Hydraulic Problems

I just acquired an Oliver 1955. I hooked up a two way cylinder and it would not extend regardless of which set of remotes I used. When pulling the lever all the way back, the detent would not lock the lever in position. At the same time, the hydraulic pump would growl. If I would pull the lever slightly back, sometimes I could get the cylinder to extend. Once moving, the lever could be pulled all the way back and the detent would hold the lever in position. When the cylinder fully extended, the detent will sometimes release the lever, and other times not. When the cylinder extends, the pump will growl. The cylinder retracts normally with no noise. The power steering, hydraulic brakes and hydraulic PTO clutch work fine.
The hydraulic reservoir was low on oil so I filled it but that didn’t change anything. Thinking the pump wasn’t getting adequate oil causing cavitation and thus the noise, I changed the hydraulic filter and oil. This didn’t help. Unloaded, the 3PT lift arms go up and down (haven’t tried connecting any implements). The pump will growl at some point as the lift arm rise. Other than the noise, the 3PT seems to work fine.
Does anyone have any tips and/or suggestions for me before I start though the lengthy trouble shooting procedure outlined in the shop manual?

Typo - Oliver 1955 not 1956

Try a different cylinder. If you have Pioneer couplers,those male tips are notorious for acting up. I'd bet even odds that you'll find one of them on that cylinder is the culprit. Does one hose stiffen up? Is it next to impossible to get out of the coupler when this happens? Those would be dead giveaways.

On my 1955 the lever closet to the seat has no detent lock. The outside lever does. It is a feature I kind of like when using both levers at the same time.