Elkmont 24 bunkhouse where are all the holes?

We keep waking up with more flys after spending an hour each night killing em all. We keep no food in the camper only thing we leave is our basic dishes.
I have screen material over the vents for the refrigerator we have removed the microwave as we don't use it. I put the camper on ramps and rolled under with expanding foam to all the gas and electrical. and i cut screen covers for the vent handles. I didn't have this problem with my popup or my big camper with a slide.

Please tell me what I have missed.

Thanks,
Jason