try draining some of the fluid from the system and running it through a coffee filter. See if you find metal.

Joystick valves are more sensitive than their two-way counterparts to contamination - just by virtue of their more complicated structure (I would think).

As I remember the design of most hydraulic systems, the pump is designed to bypass harmlessly when no pressure is required (output line fully closed).

Open the output line by toggling a valve to a device, and the bypass on the pump closes and pressure goes to the device.

Your upward creeping bucket is placing a constant demand on the pump, and that's leading to heated oil and consequently heated engine.

Get the joystick serviced - I think you might find a stray shaving has nicked a seal and is allowing pressurized oil to constantly bypass the valve and create the demand on the pump.