Hi,

You must use just ONE BEC per RX, if you use more than one BEC per RX bad things can really happen, why?

Battery Eliminator Circuit (BEC) is nothing more than a Voltage regulator that "reduce" any voltage at input for a given voltage (~5V) at output, the question is that the ~5V is a undetermined value, when you plug two BEC at the RX, each one is delivering their own voltage to the RX, the problem start here.

Example: One is delivering 5.2V and another 4.9V, the RX is "burning" 0.3V inside. More than this, today in order to reduce space and improve efficiency, most of the ESC use "active" voltage regulator "monitoring" the output and when the BEC "see" a obnormal voltage at their output, very bad things happen. My advise, remove the red wire of all ESC less one.

About the Quicrun:

Attention for the fact that the ESC have different current limit on both directions (60A Forward, 30A Backward) you must swap the motor wires in order to have the forward on both motors when the robot move forward, since the "Forward" is used harder than backward on ours purpose.

Guilherme