Your problem is from the render width of the sprite itself. Take a look at your rendered sprite in Pheonix and your 24x32 charas sprite sheet. The widths of the two are different (almost 4 pixels). Thus you are getting "Smooth Scaling" and thats not what you want. Make sure that when you render your sprites you are rendering them pixel for pixel.

Reading some of the other information, it also appears that you have overlapping pattern rectangles. Try scaling your images by hand in Photoshop to Power of 2 (I use 512x256 for Charas sheets) and see if things get cleaned up. If they do, then likely Phoenix isn't properly remembering the original image dims when it up scales the image.