I'm making a mini RC car with an Arduino nano and wireless communication with RF433, with 2 motors with 2 motor drivers (L293D). I use 4 1.5V batteries to power the arduino nano and another 6V battery pack to power the motors, and use a joystick with an Arduino Mega to send commands. I've written a program that sends specific digits when the joystick is in a certain position, i.e. when the joystick is "bent" to the front it sends a "1", a "2" is sent when the joystick is bent towards the back, and so on.
My problem is this: When I bend the joystick towards a certain direction, the RC car moves accordingly without problem; However, when I bend the joystick towards another direction (in other words send a different command), the RC car doesn't respond. I took a look at what the RC car was receiving, and I've noticed that after the first command was sent (when I bend the joystick towards a certain direction), no more commands get to the RC car (in other words the Arduino Nano). This occurs occasionally, and I can't afford to have defects like this. I think this means the Arduino Nano "froze" after the first command. Is this because of not enough voltage or current? Are there any alternatives to 4 1.5V batteries that are not pricey (I need to build 8 of these RC cars)?
UPDATE: These are the pictures of my breadboard and whole thing. Though I doubt it'll help.