Ive got a 3 year old 32xl schwing 2023 twin circuit machine that ive had since new.Lately when Im pumping on about 4 or under on the flow divider knob(especially when Im pumping real slow,about 2 or lower on the knob)the rock starts doing its own thing.What it does is when the left hand piston is coming down and get to the end of the stroke the rock will swing to the right and then just as quick itll swing to the left and then back to the right.Every second stroke this happen.What I find myself doing is turning the flow up a couple notches for a couple strokes and then back down and it corrects itself.Ive checked the mps block for damaged springs,spools or blocked orifices but it all looks good.Can anybody suggest something to me,it will be appreciated. 

Sounds very much like a problem we have on a JMBH.. (a cheap spanish assembly)

The serviceman also couldn't figure it out.. I tried with some extra revs and than lower volume but that didn't help eighter I believe.. But Soon after that I switched pumps so I didn't have a good chance to try it out..

Hey Dingo, give Jeff Popa or Jorge Gonzales a call at schwing 651-429-0999 they will be your best resource to get your problem fixed. When the phone is answered ask for either one personally.Good luck

Dingo, did you check the two check valves at the end of the MPS block? if you dont have a replacement, switch them out with each other and see if the problem goes to the other diff cylinder, then you'll know if you have a bad check valve; if you look at the schematic for the S3 spool, you see that the signal lines are connected, there is a hole drilled though the S3 spool, make sure this hole is not plugged;

Try Mick Wherritt on 0412248997, hes up in sydney and really good with schwing.