First, welcome to YuneecPilots!
Now let’s look at the problems you are having. The usual cause of a flyaway with the Breeze is a compass malfunction. Did you get any warnings in Breeze Cam when the flyaway occurred?
Did you do the Compass Calibration before your first flight?
If so, describe the area you were in while doing the calibration.
Remove the bottom cover again, being careful not to break the small tabs on the front near the camera. With the Breeze on its back and the rear nearest you, look on the left side, there should be a wire bundle coming from the GPS at the top of the Breeze. Make sure it is securely plugged into the circuit board. At the back should be a small circuit with a wire bundle, make sure it is plugged in securely and that it is still firmly mounted to the frame of the Breeze. It is the compass and must not be able to move as the Breeze is placed in any position.
Ensure all other connectors are securely fastened. Then replace the bottom cover.
Insert a fresh battery, hold in the reset button near the microUSB, power on the Breeze and continue holding the reset button for 20 seconds, release the reset button and power cycle the Breeze. If you do not get the normal rising tritone beeps and go to a flashing blue Power LED, power cycle the Breeze. If still no joy, contact Yuneec CS.