Servos pull too much current for the onboard 5V voltage-regulator.
There are a lot of circuits online that show supplying servos from the arduino 5V-pin.
This is unprofessional.
As soon as the servo has to deal with some load the current goes up and the voltageregulator shuts down => program-crash
Servos should be always supplied separately but the GND of the extra power-supply and GND of the arduino must be connected
This picture shows the principle
nRF24-modules are very cheap but are a little bit picky in communicating
read Robin2's tutorial
best regards Stefan