Hello! I have a problem on PMDG 747-400x that when I set cruising altitude in fmc and then in autopilot panel, For example FL320, the aircraft reaches to FL320 then it does not become stable on FL320 rather it goes 200 feet up and down continuously. Can anyone of you help me and another thing that is this real problem, I mean does this thing happens in real aircraft or it becomes stable when it reaches the assigned altitude?