Servo library glitch??

I build a quadcopter and I use an UNO to control it. The UNO reads out 5 channels of a 2.4Ghz receiver with the function pulseIn.

Than I transform the received data for the brushless motor driver, I use a 4-in-1 Qbrain ESC. I use the Servo library to control it. Pins 10-13 are used for the motors

One of the four engines turns significantly slower than the other three. I swapped out the engines to see if one is mechanically damaged but this is not the case.

When I calibrate the ESC I calibrate all 4 engines at once like this

motor_1.write(throttle); // throttle being servo input 0-18
motor_2.write(throttle);
motor_3.write(throttle);
motor_3.write(throttle);

Atm I dont have an oscilloscope so it is hard to read out the PWM signals.

The problem must be in either the Qbrain ESC or the servo library Could it be possible that the problem lies within the servo libary?

bask185: When I calibrate the ESC I calibrate all 4 engines at once like this

motor_1.write(throttle); // throttle being servo input 0-18
motor_2.write(throttle);
motor_3.write(throttle);
motor_3.write(throttle);

Look at your code a little closer. You have what we programmers call a "copy-and-paste error".