98 32xl 1200 twin circuit 2 accumulators. Pumped some really rocky mud, washed out and noticed rock valve shifted fine to the right but very slow and jerky to the left. Put harsh mix lever on and everything is fine. I'm worried about damage if it's left on. Tried relief cartridge located on frame rail to right of brain, by harsh shift handle, no blown O-ring or teflon back up ring. Also took apart way valve ng06, looks fine, as well as valve mounted on top of S-3 at extreme rear of machine in front of shift cylinder . Any ideas? Please keep it simple or with picture or drawing as I have hit my head too many times on boom, to understand anything too technical. Thanks!

I am assuming with "harsh mix lever" you mean the lever for the soft switch? I dont know what exactly your set up is on the truck, but there are 2 check valves or may be a shuttle valve that needs to be replaced. If you have the newer style MPS,see pictures, swap out these check valves, and see if the problems goes to the other side; you may have and older set up with shuttle valve,take it off and remove the fittings, and you will see a screw on the inside, if it is loose tighten it down (loctite), you may need to replace it completely

that didnt come out very well, those two checks are at the end of the block