Took out our new to us 2011 MPG 184 this weekend for the first time. Loved it, but the only issue we are having is somehow flies are getting inside the camper. We left for a few hours, doors all closed, and when we returned their were probably 400 flies inside. We spent half an hour killing all them but the next day have dozens more inside. We can't figure out how they are getting in. Screens are all good, no obvious areas we can see. Only thing I can think would be thru the air conditioner or furnace maybe? Anyone ever had a similar issue?