Hi again
That is the second of those screws that I know have that has worked a way loose. The guy usually responsible for that screw must be on holidays from the factory.
You have come across the good old Switch Warning. I strongly suggest that you read up the ER9X Wiki guide (there is no and never has been any printed 9X/ER9X manual)
http://openrcforums.com/wiki/index.php/Er9x_user_guideAll switches at startup must be in NEUTRAL position. Push all switches toward the back with the exception of the 3 position ID switch which must be in the middle position.
All warnings can be turned on or off in the radio setup. However I suggest keeping the switch warning on as ALL control units calibrate at startup. SO if you turned on your Tamiya tank with the MGN warning ON you would have no proper functioning of the cannon/gun fire.
Cheers
Kevin G