The whole system in picture :
That looks like a LOT of antennas near each other.
And the POWER stuff like FET on the same breadboard as the switches. Looks like trouble.
Suggest you get a metal plate as a base, and rewire all this, with Power supply, Loads, FET in one section, all the low-power things in a separate area. Suggest a bolt into the metal base next to the power supply negative with wires from the FET Ground/Source and the Arduino grounds to that common point.
OH: the Computer with the USB: You may want to connect it's case ground to the common ground point! Think about where the BUILDING ground comes into all this. You do not want multiple ground paths.
The mechanical design of something like this is as important as the electrical design, and they go together.
Get the power part working with a simple test sketch, THEN start adding the inputs, display, etc.