we're renovating our basement. picked up 2x3's to lower the point of contact on the ceiling for drywall. they were straight when we brought them home, next morning... warped and twisted.
construction lumber is very wet, in terms of lumber. some of it will even leave a moist feeling on your skin while moving it. It's just a fact that that stuff bends and warps as it dries.
but, so many folks have used it, and their tanks are still standing and still level.