Glad you found your problem and good luck with the mice. We can't use bait dut to the dogs.
We lived in the city for ~30 years had during the ~20 years we had motorhomes there never had a mouse problem.
We (I mean my wife) then decided build a new house in the country on a heavily grown up lot. I spent a year clearing the property and then we started to build. At the point I started to install plumbing and wiring I pulled the motorhome onto the lot and started staying in it for security.
That's when the fun began, mice. I had mouse traps set, caught some but there were many more. Had some success using the mouse deterrent that smells like peppermint, I put some of these up in the ceiling.
Well we (I mean I) mostly finished the house and I had the motorhome parked on a large gravel pad where I intended to build a garage. In 2020 once I got the house done I moved my attention to building the garage and had to park our (I mean mine) coach off to the side in a grassy area and the mice were back with a vengeance.
Guess what they like to eat, the wires on ear buds, I had an accumulation of them in my bedside drawer from traveling. The mice probably chewed up a dozen pairs. I have not found any other wiring problems yet but it's only a mater of time.
Once I got the pad poured and while I was waiting for the garage to delivered (~3 months) I moved the coach onto the concrete and spend a week cleaning out the entire coach and found multiple nests. One mistake I made was leaving some food stuffs in a cabinet the mice could into. The upper cabinets we fine.
At that point I bought a large bag of mothballs (yes they say that they don't work but I was desperate) and put multiple pouches in lower cabinets, drawers and cubby holes in the living area but not in the basement. I have not caught anymore mice in the living area and only one in the basement.
The downside is the smell of the mothballs in the coach but I intend to move the pouches to the basement once we ( I mean I) get ready to leave on a trip.
But I finally got my garage done and the coach will have a pretty secure parking area.
2002 Monaco Windsor 38 PKD Cummins ISC 350 8.3L
2005 Jeep Grand Cherokee w/5.7 Hemi