What do you mean "trips the Arduino overcurrent sensor"? If it's the one in the MGNZ code, using the current sensor they recommend? That shouldn't trigger that low, but regardless, you can edit the code and raise the current limit if you need.
Checking the SSR is a good idea. Those can be junk.
Lastly, you may need shielding. I'm fighting an inductive noise problem right now in my setup that causes my arduino to freak out and reset. Consider shielding the control board, and putting chokes on various long wires to dampen the EMF in the circuits. The noise coming out of the inductive circuit might inulduce voltage who knows where, and with all the digital signals going to servos, displays, etc stuff can get messed up. Doesn't take much either since everything is usually 5v max on the control side.