Electrical, but which part? The high limit cutout could do this and a "smack" clear the contacts. Suburban high limit switches commonly have that issue but usually on older units, not brand new ones like you have. The circuit board or connections to it could do that. However there are a lot of possibilities with the circuit board and components on it.
The sail switch would not cause it to not run at all, only not light, so you can rule that part out.
I would check all of your connections again, making sure the thermostat wires are well spliced, as well as the 12 volt
input and the GROUND. Grounds are commonly an under investigated source of problems. The "faint buzz" you originally had still sounds like some contact is not good, and there is a high resistance in the 12 volt
Then, pull the plug to the circuit board and slide it back on several times, to clean the contacts.
The fan motor could be defective, I guess, and that could also cause the "faint buzz". A smack to the case might get it started, but not real likely.
If it is still not working right, call Suburban for help, as it is a new unit.