POSKY 737-700: low oil pressure

I am using the POSKY 737-700 with the standard 2D and VC boeing cockpit. When entering the plane, the engines are already running (so no cold&dark situation). Taxi to the runway not a problem. But after takeoff, the enginedisplay give the errormessage 'low oil pressure' and the plane crash in the woods...... Sometimes the plane give also the errormessage 'start valve open' when i am at the gate, but not always....... Do i missing something here?