Bukkit

the default items do not show up, when a player joins the server and automatically goes to the main lobby.

And when a player goes to the main lobby by using the hub menu, the default item do show up. (there are no errors showing up in the console logs)

disallowHubCommandNoPerm: true
Settings:
  Enable_Per_World_Inventories: true
  Enable_Per_World_Ender_Chests: true
  Enable_Teleport_To_Spawn_If_Same_World: true
  worldselector:
    ==: org.bukkit.inventory.ItemStack
    v: 1976
    type: NETHER_STAR
auto-update: true
Version: 3.7.98
Worlds:
  world:
    name: world
    spawnLoc:
      x: 61.5
      y: 64.0
      z: 61.5
      yaw: -269.53955
      pitch: 90.0
      w: world
    weatherstate: NO_RAIN
    i: 0
    gamemode: SURVIVAL
    color: 0
    hidden: false
    canuseportals: false
    isMainLobby: true
    material: EMERALD_BLOCK
    displayname: Hub
    disablehealthandhunger: true
    defaultitems:
    - ==: org.bukkit.inventory.ItemStack
      v: 1976
      type: NETHER_STAR
  scouting:
    name: scouting
    spawnLoc:
      x: 80.5
      y: 64.0
      z: -395.5
      yaw: -222.81323
      pitch: 90.0
      w: scouting
    weatherstate: NORMAL
    i: 2
    gamemode: SURVIVAL
    color: 0
    hidden: false
    canuseportals: false
    displayname: VW & O
    material: OAK_LOG
  public:
    name: public
    spawnLoc:
      x: 0.5
      y: 83.0
      z: 0.5
      yaw: -90.22687
      pitch: 90.0
      w: public
    weatherstate: NORMAL
    i: 3
    gamemode: SURVIVAL
    color: 0
    hidden: false
    canuseportals: false
    displayname: '"Public Survival"'
    material: GREEN_CONCRETE

Hello Neoje,

I believe I know what is happening. Default items are currently only applied when a player changes worlds, and currently does not check when a player joins. This will be added in the next update.