We identified the issue and it’s caused by our conversion from PNG to JPG, which is run to optimize textures download in the viewer. When you upload a texture in the editor (or with a model), our servers generate an optimized version of it at different resolutions to be used in the viewer.
For small resolutions ( <= 512x512) the JPG quality parameter used is currently 95, which works most of the time but not in this case. The resulting JPG palette has slighly different colors and the diff is noticeable since each pixel is spread across big areas in the model.
Using a quality setting of 100 seems to do the job but we need to investigate to see if we could update the rules for this specific usecase.
We 'll keep you in touch if anything is done regarding this issue