DIAGNOSIS The 5-way joystick/navigation button is the only control on this monitor, and its placement means it's easy to press accidentally when you're handling the stand. It's not broken, just a design quirk you have to work around.
FIX When adjusting the tilt, don't grip the monitor from the bottom center. Instead, place one hand firmly on the top edge of the monitor bezel and the other on the back of the stand's neck. Apply gentle pressure to tilt. Your fingers will be nowhere near the joystick. To move the whole monitor, lift from the base of the stand, not the screen.
IF THAT DIDN'T WORK If you find yourself constantly bumping it, you can get into the habit of immediately canceling the menu. A quick, short press of the joystick in any direction will bring the menu up. If you do it by accident, just press the joystick straight in again (like a button click) to exit the menu without changing any settings.
HEADS UP Be careful not to push the joystick sideways with excessive force. It's designed for navigation, not as a handle. Repeated hard lateral pressure could potentially damage the internal switch over time.