5 V input not working properly

Hello, i have quadcopter controlled with Arduino uno. When i power arduino from USB port all is working OK, but if I power arduino from regulator BEC (5.3 V source) only two motors are working . Output from regulator BEC is connected to Vin PIN.
Any ideas ? thanks in advance

"regulator BEC "
What is this?

Show schematic.

You need at least 7.5 volts on the Vin pin.
Use the +5 pin if the voltage is < 5.5V

Regulator have 3 wires . One for signal, one ground and one is +5V . Ground is connected to Arduino ground and +5V is connected to Vin PIN . I tried connect +5V to Arduino 5V output, but same problem .

When connected to the 5 volt pin use a DVM to measure this voltage.

What is the measurement?

Show us a good image of the wiring.

.

When connected voltage is ± 5.2 V .

Schematic : Red line (5 V), Black line (GND), Green lines mean signal wires

+- :o

Show us a good picture also.

Voltage is approximately 5.2 V, you have picture in previous post. What you dont understand on the picture ?
+5 V to Vin, GND to Arduino GND. Simple.

That is a Fritzing diagram.

Take a picture with a camera.

I tried connect +12 V from Li-Po battery to Vin PIN but same problem . Image is in attachment .

If you have access to a oscilloscope, can you check for noise on the power supply.
.

If you are satisfied that the power supply is good (neither your fritzy nor the photo or the board show the power circuit well) then it might be the board. While is resembles an Arduino UNO, it's actually a clone. Can you run a simple sketch on it using the 5V and GND pins for power?