@Varilyayou had this same issue too until I realized I have to be on vrc avatar sdk 3.7.3 and unity 2022 for it to properly upload without any errors, anything lower than that will give you a compiling error and not let you upload it because the avatar runs on pcs 8.0+
Have you checked the texture size? There's a chance that the image might be larger or smaller than the texture you are currently using, that would potentially change the position of things when you try to combine them