Weird behavior with servo motor
 

Hello guys!
(My source code is here and the board design is here)

I'm starting my first real project with Arduino. I'm attempting to build a RFID cat feeder so my fat cat stops eating the other ones's food.

The principle is simple: if no RFID tags are detected, the servo motor will move to the open position. If a tag (the fat one's) is detected, it will close.

The issue i'm having is: whenever a tag is detected, the motor starts to behave strangely.

I'm using an Arduino Nano, a servo NG90 and a RDM6300 for RFID.

Everything is connected to the Nano via protoboard and the Nano itself is connected to my PC via USB-C.

Thanks!