I think foamy fluid is normal for these systems. I had to replace the leveling valve on my wagon about a year after replacing the accumulators. You bet the fluid was highly aerated when I opened the bleed valve. There's no provision to bleed the air out of the lines between the leveling valve and the accumulators, so I'd kinda expect it. As well the fluid & air is under high pressure, so when you release it to atmospheric pressure, the trapped air is going to rapidly expand, foaming the hydraulic oil.