Insulation Entry Point
New home construction with this kind of overlapped notch are classic examples of mice entry points. I had to pull back vapour barrier and insulation untill I found it and matched the location to the pipe outside. Note the 2 droppings near the washer.
Once this hole was found and sealed the mice could no longer get in. I found it by noting the droppings from the basement notch out for the home framing.