I had mice entering the RV also. They were in the bathroom, bedroom and near the dinette area. I caught 2 of them with mousetraps, and after an extensive search I found their path in.
The attached photo is the area under the bed. Where the arrow points to the green circle is where electrical wires come inside. There was a about a 1/2 hole where I could see daylight. I patched the hole with steel wool and foam. The mice had even built a nest in there with toilet paper stored under the bathroom sink. After doing this 2 years ago, I have never had anymore problems with them
I didn't notice any evidence of them in the cab area. Who knows, they probably checked that out as well.
2016 Greyhawk 31DS
2016 Chevy Equinox LX
Blue Ox Baseplate w/Aventa LX Tow Bar & KarGard II Deflector
Blue Ox Patriot Brake