A common error made by new quest designers is to set Warps to the incorrect (x,y) coordinates. New designers often use the coordinates they see displayed at the bottom left of the editor window as the destination for the Warp. It is not that simple.
Most Dmaps, except for Overworlds, are smaller than an entire Map. Maps are universally 8x16, whereas most Dmaps are 8x8. So, when you set up your Dmap, you can shift it left or right over the Map to cover the Screens on the Map you want.
This means that the (x,y) cooridinates of a Screen will be different depending on whether you mean the Screen's Map or Dmap coordinates. If you shifted your Dmap over 8 screens so that it covers only the right hand side of the Map, all Screen x-coordinates in that Dmap will be 8 less than the x-coordinates for the same screen that you see on the Map editor.