debugging misbehaving arduino's over video call is the fucking worst, especially when the people with the arduino on the other side have 0 experience so far
@f0x servos can generate a lot of interference voltages to which serial communication is very sensitive, if I'm correct. have you tried adding an extra capacitor near the servo? or does the serial communication not work even without the servo?
@adb still not what is actually wrong with it, impossible to debug remotely like this. device just would not show up under serial ports while the servo was connected, but it wasn't brownout either (and the servo wasn't moving)