GUI items ignore datapack item_model, only show vanilla icon

[crimson plover]

When using item_model (or the minecraft:item_model component) to reference a datapack/resourcepack model (e.g. gbg:gun/standard/pistol), the model shows correctly when given to players via commands or functions, but DeluxeMenus GUI displays the vanilla icon (crossbow). The item_model value is stored internally but not visually rendered in the menu GUI.

Environment:

• DeluxeMenus version: 1.14.1+
• Minecraft server: Paper/Spigot 1.21.4
• Gamingbarn datapack + resourcepack loaded on client
• Client: Vanilla 1.21.4 with resourcepack active

Steps to reproduce:

1. Confirm /give @p minecraft:crossbow[minecraft:item_model="gbg:gun/standard/pistol"] shows the custom pistol model in the player hand.
2. Create minimal DeluxeMenus YAML:

menu_title: "Test Menu"
open_command: testgun
size: 27
items:
  pistol:
    material: CROSSBOW
    slot: 13
    display_name: '&cStandard Pistol'
    lore:
      - '&7Basic handgun'
      - '&ePrice: $1200'
    item_model: "gbg:gun/standard/pistol"
    left_click_actions:
      - '[console] function give:pistol'
      - '[take_money] 1200'
      - '[sound] ENTITY_ITEM_PICKUP'
3,Reload DeluxeMenus and open /testgun in-game.

Observed behavior:

• GUI displays a vanilla crossbow.
• Clicking doesn't give anything

Expected behavior:

• GUI should display the custom model identical to /give.

What I tried:

• Tried different item_model syntaxes (with/without quotes, under item_components).
• Reloaded/restarted server, cleared client cache (F3+T), relogged.
• Verified DeluxeMenus version >=1.14.1 and no YAML errors.

Notes:

• Resourcepack model works in inventory.
• GUI rendering fails for custom datapack item_model.
• Functional workaround: accept vanilla icon in GUI, actual item given is correct.

[crimson plover]

Still no support, I need it asap