Governor valve safety fluid pressure hunting

Hello to all,

I have one question regarding on Safety fluid pressure on governor valves. Whenever HPGVs open rapidly, there is a drop in Safety fluid pressure. Then we assumed, this could indicate wear in the Electro-Hydraulic Amplifier (EHA) blocks.

We took out the valves and overhauled but still the safety fluid pressure remains hunting..

What other possible factors that could affect this problem? thanks.