I have a H50D that the lift and tilt slow down after it heats up intermittently.

Serial H2X394A00401 Engine is CBJB

side shift and the fork positioner do not seem to be any different.
I checked with pathfinder to make sure that the lift and tilt are set to 100% for the speeds.

The engine still revs up like it should when moving the levers.

The engine has been replaced recently. I have also replaced the two valves that are on the end of the hydro static transmission. The issue did not change with the valves.

Is there a priority valve that we are missing or could it be a worn out pump?

Anyone have any information on this issue?

Thank you in advance