I have a RT 600e. I don't think there is hydraulic disconnect on those for roading, like the older RT's have. I would suspect the pump coupler possibly failing. It would be worth checking making sure you have good power for the coils upstairs, no voltage loss. And installing a pressure gauge so you can see if it's dropping out pressure when you are loosing function, vs loosing electric. You are just going to have to start narrowing it down, and testing and gauges are the way to do that.