Sounds like an error in tillering and not in the wood itself. I don't mean to be sounding like a turd, but have you built a bow before or is this your first?
Tiller slowly, take a couple scrapes, check the tiller, and repeat. The quickest way to ruin a bow is to rush. First get the technique down, hen you will get faster as you get more experienced.
What are you using to tiller? My recommendation is not to use power tools until you've got a few under your belt. I prefer to use a draw knife, farriers rasp, half round rasp, half round file, chainsaw file (for nock grooves), scraper, and sandpaper. A lot of guys also like a spokeshave. You could probably get by with less, at minimum a rasp, a file, a knife, and sandpaper.
Also if you post pictures and ask questions along the way of building, thee are lots of people happy to help you out; good advice can be the thing that saves a bow.
Lastly, anytime yu have a bow that starts to bend too much in one spot, you need to fix that before you go any farther or it will just get worse and worse. A hinged limb is almost always fatal to a bow.