The valve in the main valve block that feeds the side shift & tilt function is NON replaceable - it would be a complete replacement main valve block.

When was the hydraulic oil & filter last replaced?

I have come across RRE before where hydraulic oil & filter has been replaced by an in house technician & someone had removed the complete filter assembly & just fitted the replaceable green coloured element insert back in to the tank but without the metal outer jacket.

That in turn trashed the hydraulic system with debris when the filter element exploded.