I'm a fat old lady. My home is old and it has a crawl space under it. I had this problem a few years ago and I crawled under there with a shoebox holding a hammer, nails and ends of cans. I'd taken several cans from my recycle box and cut the ends out and nailed them over places that looked like cracks in the old flooring. I have some carpet and some vinyl over hardwood, but at the edges where the quarter-round molding is, there are warps. My house is pretty tight and dry but there has been more settling. This house was built in 1947, so you'd think it had settled right much by now. But, there are things, like pile driving for new bridge supports not far away, jet planes with sonic booms that create vibrations that 'could' make settling. So, you might have to find the cracks, or put rubber boots around pipes and cables or whatever enters your home. They are sneaky little critters. The day I decided to crawl under my house, I'd taken the laundry basket to the bedroom and one jumped through the webbing in the basket and I snatched it and bashed his tiny little head. It was an instant reflex that made me sick. I never would have thought little old me a killer!! UGH i should have called the pest people.
I need some blessings, here.
Ruth