If things disappear after you save them, it's possible that the save configuration that you chose wasn't compatible and caused corruption. I just tried saving the TM file as a DXT5 and it ended up corrupting the image. Anyway, when I first edited NM of the Dark Buckler, because the color wasn't the same used in the rest of the NM files, it didn't work and caused the item to look very bland and dark in-game. It doesn't matter the angle I chose, half of the shield would look pitch black and the other would look very dark, almost flat. i thought it was the CMM so I tried tweaking it without success, but once I restored the original NM file, it recovered its color. After adjusting the color of my custom NM file to match the rest of the NM files, it worked.