STICK EMI is a reference to the controller sticks getting Electro-Magnetic Interference.
The RC sticks uses Hall-Effect sensors. If there's a source of magnetism near them, or parts of the controller have been magnetised, it'll show the STICK EMI error.
Move the controller away from anything else and restart it. If that doesn't resolve the issue, let us know.
At least, that's from what I understand. msinger will know better!
Heads up for anyone trying to resolve this problem.
Rub a magnet on the back of the controller and the sticks. It'll fix it.
It just means you've disturbed the magnetic fields in the controller (happened to me after leaving the controller in my bag next to my ipad), so rubbing the magnet resets the fields