Recently, I've made an Aternos server with my friends and it's all working fine, except for the fact that when launching on the server specifically, the second layer of our skins disappears. This occurs only on the server as the skins still appear just fine when the same modpack is used on singleplayer mode.
Is there a setting I'm not pressing in the menu screen for Aternos or something, or is there a mod made to counter this problem? I'm using Forge 1.18.2 and Optifine. I've heard about skin restorer but that's only a plugin, not something for Forge.
Edit: It seems that the skin is loading as when I die in the GraveStone mod, the second layer of the skin appears on the player's head. So it seems like Aternos is doing something that makes the second layer invisible.