My dealer has been on phone with terex and they can't figure out whats going on . I have a hr-16 terex 8000 lb mini 1400 hours . All controls operate fine for 10 to 15 minutes then it gets jerky . when swinging boom side its a little noisy too . All controls still work , pressures stay right on where they should . Pump has been off and inspected and all good . They say I needed a relief valve got it , no different . Then check valve , got one , no different . Anybody with any suggestions please respond . Been at dealer 10 weeks