1. turn on normally, get gps and ready to fly
2. turn on motor ok
3. then i turn it off change batt
4. then get gps again ok
5. but after that motor wont start anymore but led show it's ready to fly

Have you had it apart top off at any point if so check your  soldering points feel the motors  are they hot unplug the battery wait a few sec and plug it back in not sure but try it and let us know