I believe I MAY have found the point of entry.
The generator opening--no generator in it--has walls that do not go up the entire height of the compartment. Also the lock does not work well and there is often a gap when I don't force it closed. Additionally, I put a mouse trap with obviously too little sensitivity in the area. The peanut butter was eaten off the bait holder and the trap did not snap.
This area corresponds to where I believe they are gaining entry.
I bought some aluminum screen material and plan to cover all the areas with screen, once it stops raining/storming. Also bought a couple of live traps that should catch them just by entering.