Had an operator hit the E stop button now the pump won't come up to pressure. Done a service on check valves and dynamic seal. Still no joy. Replaced pcv poppet and seat with a used one and also changed pcv kit. Run ok for about a day and now dropping pressure. Run pressure calibration and now cutting head flow water for a few minutes then stop flow but can hear air from the cutting head and calibration continues. Changed settings in icscard but still not coming to pressure. Changed pcv poppet and seat again to a new part and now can't get pressure calibration to work probably. Can anyone help Thanks