There are times when a print warps or will not print flat - here is a solution:
Prints that take up a large surface also have a higher tendency to fail. If you find that warping is occurring frequently on a print, spray Aquanet Hair Spray on the surface of the build plate.
Note: This is the strongest and most used among 3D printing enthusiasts, but most strong hold hairsprays will do the trick if Aquanet is not available