That was happening to me. After several days I found my problem.
The wires from the battery to the 3-in-one, where it was soldered to the battery connector was only held on by two or three strands. At point 3 listed below.
So going from the battery:
1. Battery
2. connector on battery
3. connector on wire
4. wires
5. 3-in-one
Fixed the connection / wire. Problem gone!
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A lot of RC stuff:
Heli's, Quads, FPV gear, Tools, Chargers, Transmitters 
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