If you already have the motor and want to do the repair yourself, once you pull the "plug", the screw is a not so common one type of tork called the star.
A buddy of mine was flying this past weekend and the app disconnected. Further troubleshooting proved the cable connected from the controller to the Tripletek was faulty.
Don't mess around with a dead battery. Even a good battery needs to be supervised while charging. Charge it outside where you won't risk your house or anything around it. Ask me how I found out.
I have the A7. Works perfectly. Need a 10-12" cable and a tablet holder you can print on a 3D printer. No problem with DJI FLY as others have reported.