Resting= cooling the hyd fluid which restores some viscosity from the hot temps you described.
No expert here, but I would make sure the fins on the hydro are clean.
You could try changing the hydro oil and it might buy you some time to decide if you want to go with a new hydro on that side or trade it.
it sounds like that hydro is on the the way out.
but If it were me, I do some more googling to see if they have known problems, maybe some one else here has experience with that model hydro.
obviously they don't build the quality like they did yesteryear, but I don't know the hour life expectancy of them.
