I m having trouble with Volvo I shift , it 2006 build, when Truck is on hill it changes the gear, display shows gear changed but Truck won’t move for two seconds, then it suddenly starts moving with a jerk, by the time after two seconds speed gets slower, it start changing the gear again, does it again n again until it stops. First mechanic change d pwm valve, re calibration, still does same, then Truck went to volvo they changed clutch and cylinder, air pressure switches, tried another gear Ecu, software updated, still same , anyone please suggest what can we do?