Power management
We always recommend to use the X0 port with a dedicated BEC power rail. The servos can demand a very high load on the entire circuitry. Especially when acting all togheter, the current load can spike up to several Amps.
If the circuit is unable to provide high currents, the voltage will drop and most likely the module restart or act in unpredictable ways. Another side effect of voltage drops is servo stutter. This can also happen when there is a bottleneck in the circuit (e.g. thin copper traces in the receiver), even during idle.
The module is designed with a huge 5V power distribution rail, which is able to sustain peaks and higher Amp rates.
When using ESCs as 5V source, you may use a Y-servo cable and connect one end to the receiver while plugging the other end into port X0. The PWM pin on port X0 is only physical but not logical.
Also check that the ESC is able to deliver enough current in order to power all 4 servos at maximum peak.
Passing high currents through thin copper traces (e.g. some receivers) can irreverrsibly burn them.
Electrostatic discharges can damage the module and/or corrupt the firmware.