The nuance of this issue likely revolves on the fact that for some reason, a higher voltage level is received by the motor due to a possible malfunction of a resistor. This is yet to be fully assessed though, issue might come from a completely different reason.
In the meantime, on my last PR, a line was placed that makes the second motor (centered motor) to move 15 units less. Obviously this should not be treated as a solution, but rather as a band aid to prevent the motor functions to completely breaking down.
// lib\motors\motors.cpp
void Motors::Motor::setSpeed(float speed) {
/* ... */
if (id == 2) pwm -= 15; // ****Calibration for motor 2
/* ... */
}