Try to always save it over the skeleton file (always **AA, the first one). When adding new parts and textures it'll say something else, probably the last opened file, so always find the location of your model and select the first file. The battle models are retroactive, so if you change the skeleton file name (RTAA-RDAA) it'll change every file name for the model, so it's also very easy to overwrite other models if you aren't careful.