Unable to Change Arm Size for Character (Possibly a Bug)

I'm currently unable to change the arm size (from normal to slim) for my character in the Dressing Room. I'm using one of the new default characters (Ari), and even after removing all cosmetic items and accessories, the option to switch to slim arms is still unavailable or grayed out.

I've tried the following steps:

• Removed all worn accessories (including headgear, body, and emotes)

• Created a new character from scratch

• Restarted the game and checked for updates

None of these solved the problem. I'm wondering if this is a bug with the new character models, as I was able to adjust arm size using Classic Skins but not with these newer base characters.

— Thank you