[1.21.7] All Player Heads Appear as Steve Heads with ModelEngine R4.0.9-2150

After updating to ModelEngine vR4.0.9 on a Paper 1.21.7 server, all custom player heads (via HeadDatabase, DeluxeMenus, or vanilla give commands) appear as default Steve heads in GUIs. This issue does not occur on Spigot, only on Paper-based forks.

Steps to Reproduce:

1. Install ModelEngine vR4.0.9 on a Paper 1.21.7 server (in our case: Leaf 1.21.7-18).

2. Use DeluxeMenus with the following configuration:

   menu_title: "test menu"
   size: 54
   update_interval: 1
   items:
     HDB-Heads:
       material: hdb-58699
       slot: 10
   
     Vanilla-Heads:
       material: head-boy0000
       slot: 11
   

3. Alternatively, open /hdb from HeadDatabase or run a vanilla give command like:

   /give @p minecraft:player_head[minecraft:custom_name={"text":"Yoshie","color":"gold","underlined":true,"bold":true,"italic":false},minecraft:lore=[{"text":"Player Head ID: 62391","color":"gray","italic":false},{"text":"www.minecraft-heads.com","color":"blue","italic":false}],profile="Deano999"] 1
   

4. Observe that all heads appear as Steve.

Expected Behavior: Player heads should show their correct skins (custom texture based on the UUID or profile name), not the default Steve skin.

Actual Behavior: All player heads render as default Steve heads, regardless of configuration or method used to generate the item.

Environment:

• Server Type: Leaf (Paper fork)
• Server Version: 1.21.7-30-ver/1.21.7@a9c1050
• ModelEngine Version: R4.0.9
• MythicMobs Version: v5.10.0-SNAPSHOT
• PacketEvents Version: v2.9.0+a198f0e8d-SNAPSHOT
• UUID Version: 4 (Online Mode)

Logs & Resources:

• Server logs: https://mclo.gs/e9kerMX
• Screenshot (head issue): https://i.imgur.com/so1KB4E.png
• Discussion reference: https://discord.com/channels/213109157983813633/1391409221970694294

Additional Notes:

• The issue is reproducible on Paper forks (Leaf), but not on Spigot.
• It may be related to recent changes in minecraft/items/player_head.json as pointed out by a user.
• Likely related to how ModelEngine handles item metadata or internal profile resolution since the update.