During the last month on a couple of flights with the cessna it goes out of control. I'm using the auto pilot. All of a sudden the it wants to climb. The only way to stop it is to cut the trottle until it comes down. Even then it is hard to control. Once I get it back to the altitube, I can't use the altitude hold to keep it there nor will the stay on the heading. I also noticed the heading on the GPS was different from the where the heading bug is sit. I don;t know if there is an issue with the GPS or the auto pilot.