Let’s talk about Chemolube H Special Fluid. The biggest problem with seals is that this fluid is not compatible with seal material such as a urethane based material. It is also not compatible with VITON. Seal material should be BUNA (Nitrile Based). Also, the SHC526 may require complete change of every seal in the system so existing seal material must be verified.
50 Degees C is a fairly high ambient for any type of fluid so a cooler should be utilized. It is important to install the cooler in the correct part of the circuit.
Sticking servo valves is almost always caused by fluid contamination. Have you completed a fluid smaple analysis to determine ISO cleanilness rating?
Who is manufacture of your system?
You may contact me directly in needed.
Slide Valve Control Guy