Power steering quits then starts again

I have a 98 wrangler that’s has intermittent power steering issues. The first time it happened we were attempting a steep muddy climb (about 60 deg incline). After several attempts to climb the hill, the power steering stopped working. Checked the fluid, and the level was at the full mark but appears to have bubbles in it. So caulked the issue up to the steep bouncy incline allowing the pump to such air.
While limping the jeep home we passed a little muddy run that I could not say no to. After a hard run, 4-5k rpm, The power steering started working again.

the same thing happened again yesterday, only this time the terrain was relatively flat.
Any suggestions on where to start?

 

PS operates under intense pressure. Sometimes the metal lines or hoses or o-rings may have minor cracks or perforation from rust that can leak under excess pressure or odd angles

 

Entrained air may be part of the problem but I think a bigger issue is the heat build-up in the system that thins the hydraulic fluid that makes both the pump and steering box less efficient. I have had the same problem with the JK when in the rocks. I'm using Swepco 715 in it now and things appear to have improved it a bit. A PS cooler is a must if you are working it hard and an oversized reservoir is a big plus. If I was actually thinking I would keep the JK, there would be a PSC big bore box and maybe their pump on it but that is a big bite in the butt for something you would like to get rid of.

Most PS systems operate at 1200-1300 psi and anything that is going to leak will be very obvious, at least on the pressure side. A leak on the return would only affect it if it caused the fluid to run low. The return still has some positive pressure on it so you shouldn't get contaminants in the fluid.