I solved this problem.
1. Upload Minecraft save data to Nintendo cloud backup.
2. Remov all Mincraft game data both save and soft.
3. Re-install Minecraft soft and download saved data from cloud.
4. Logout Xbox account and clear login data.
5. Re-login Xbox account and restart Minecraft.
Then you can change skin of 2nd player's.
takjoe
I solved this problem.
1. Upload Minecraft save data to Nintendo cloud backup.
2. Remov all Mincraft game data both save and soft.
3. Re-install Minecraft soft and download saved data from cloud.
4. Logout Xbox account and clear login data.
5. Re-login Xbox account and restart Minecraft.
Then you can change skin of 2nd player's.