A flip was abandoned (ERR FLIP-2)

What ArduPilot says:

• ERR FLIP (Subsys 13)

Flip mode gave up and returned to the mode it came from. It does so when the roll or pitch stick is held almost fully over (beyond about nine tenths of its travel), when the motors are disarmed, or when the flip has taken longer than 2.5 s. A slow flip usually means too little height or thrust to rotate quickly: start higher and with more throttle.

Where to do it:Setup & Tuning Guide