electraguard

When I open a WEBP file that contains various signs and I use the rectangle select function over one of the signs and then either fill it or delete it and then import a different sign in the layer menu then move it to cover the filled or deleted section and then save it as the same webp file the filled or deleted sign show through the new sign. You can see the shadow of the old sign in this picture> I have tried all different kinds of thing to stop this but nothing work,