Bobcat 322 mini excavator hydraulic issue

[Waveslayer]

My old neighbor has a Bobcat 322 and the hydraulics quit after 15 minutes of run time then its back to normal in a hour or so for another 15 mins until the hydraulics quit . The blade functions still but the joystick hydraulics slow down and then stop completely within a few seconds including travel as well. There is power at 2 of the 3 solenoids at the manifold with the yellow zap strap 2 speed not working though he tells me that hadn't worked in years. There is still pressure at all 3 pump chambers but when I put the test gauge on the manifold test ports neither has pressure when the failure happens but obviously have pressure when the hydraulics are working for that 15minutes. The pressures when maximizing cylinder travel hit 2300psi. I am a little stumped as to what to check next.
Cheers
Steve