I have built my first drone (f450, pixhawk fc, Racestar Metal 4 in 1 esc), but I have an issue with the ESC. When the FC sends a signal to rotate motor A or C, it works fine. When a signal is sent to motor B, nothing happens. And when a signal is sent to motor D, both motor B and C starts to spin. The solderings are good, the FC sends a good signal. What is the issue for this? Is the ESC faulty?