Not sure why this is only happening in the SEA arenas, but the completely new skins have "invalid skin number" error popups when selecting them.
The updated skins display properly with the new version. All skins display properly in the MA.
Also, the "skins.res" file will occasionally delete itself when entering the SEA arena. So far this has happened every time I have entered the SEA first after launching the game. Entering the MA first seems to prevent the file from deleting. When the file does delete itself, the skins list is completely empty. Going to the hangar in the MA after relaunching the game might generate a new "skins.res" file when changing planes, but this has not happened every time I tested it. It may take a few attempts at restarting the game to get it to work.