The autopilot light remains on, but the VNAV switch disengages and the aircraft will just randomly start climbing. This happened 3 times in flight. SP1 is installed as well as the 600/700 expansion.edit: This also happens when I use the space bar and mouse to look around the cockpit. at this point the yoke will pull back. (mouse yoke is off, I checked)

Are you using a hardware yoke?

As far as Hardware, Im using the Logitech Attack 3 joystick and CH Rudder Pedals.

I'm not familiar with that stick, but it's possible that it might be sending a signal spike which the plane is reading as pilot intervention.

You can go into the options and choose " Realistic Autopilot" and disarm it. I have to on mine. No matter how I calibrate my hardware there is something disarming it.

Often times, people set their takeoff trim on an external trim wheel, which will remain unnoticed until it sends a spike. The AP sees the spike as a new command and tries to reset the trim to what the hardware is dictating (as set prior takeoff), which then kicks off the AP. If you reset the AP, it'll stay on until a new spike crops up. Rinse, repeat.Junk in, junk out. Always pay attention to what you and your hardware are telling the computer.

Don't ask me why because this is really stupid lol. But once I had one of my hat switches assigned to the Autopilot when pushed to the down position. Did not like this so I changed it. But I forgot I left it assigned in FSUIPC under buttons. So when I later Assigned the Hat Switch to Zoom in and out, well you can guess what happened right? Everytime I went to Zoom it would Zoom in and out but the Autopilot would disconnect.So the point of my stupidity story is to check your button and axis assignments in addition to checking for spiking. You might have VNAV assigned somewhere and forgot about it like I did with the autopilot.