Texture Messed up on Import (Gaining weird blocks of color everywhere)

Hello,

I have a png texture that looks like this in gimp. When this texture is imported into Unity, even with no compression, it gains weird "blocks" of color in places that ruins certain "sprites" within the image (for instance, look at how the hair piece has suddenly gained half of a face).

I have toiled at this for awhile with different settings. Any advice you can offer would be appreciated. Thank you!

EDIT: The initial failing .png file was created via Unity's Texture2D.EncodeToPNG function. I've discovered that the image imports perfectly if I first open the image in Paint3D, and do nothing but re-save the file. Could it be that Unity is incapable of importing image files that it exports?

EDIT: My code uses Texture2D.EncodeToPNG, which is deprecated. I switched it out out for ImageConversion.EncodeToPNG, and the image still doesn't import properly.