I've looked throgh the code to fix them before, and afaik it's to do with the code dictating the specific armour pieces these weapons are made out of. This tricks the troops holding them into thinking that the weapon isn't throwable, even though it is. This is the relevant piece of code for the Pilum:
Code:
<CraftedItem
id="imperial_throwing_spear_1_t4"
name="{=rkqaCud5}Pilum"
crafting_template="TwoHandedPolearm"
culture="Culture.empire"
modifier_group="polearm">
<Pieces>
<Piece
id="spear_blade_38"
Type="Blade"
scale_factor="90" />
<Piece
id="default_polearm_guard"
Type="Guard"
scale_factor="100" />
<Piece
id="spear_handle_14"
Type="Handle"
scale_factor="90" />
<Piece
id="default_polearm_pommel"
Type="Pommel"
scale_factor="100" />
</Pieces>
</CraftedItem>
Afaik, ALL melee weapons in Bannerlord are created out of individual parts, using the smithing system. Specifically, I believe the problem is in the weapon part
spear_blade_38. Relevant code:
Code:
<CraftingPiece
id="spear_blade_38"
name="{=nr3K4od2}Pilum Head"
tier="4"
piece_type="Blade"
mesh="spear_blade_38"
length="23.7"
weight="0.0744"
excluded_item_usage_features="swing">
<BladeData
stack_amount="2"
physics_material="wood_weapon"
body_name="bo_spear_b"
holster_mesh="throwing_spear_quiver_3_2"
holster_body_name="bo_throwing_spear_quiver_3_2"
holster_mesh_length="96.8">
<Thrust
damage_type="Pierce"
damage_factor="2.5" />
</BladeData>
<Flags>
<Flag
name="BonusAgainstShield" />
<Flag
name="NotStackable"
type="ItemFlags" />
</Flags>
<Materials>
<Material
id="Iron3"
count="1" />
</Materials>
</CraftingPiece>
And here's the code for
spear_blade_35, which is used for the Jagged Throwing Spear:
Code:
<CraftingPiece
id="spear_blade_35"
name="{=ZUp9mm79}Jagged Spear Head"
tier="3"
piece_type="Blade"
mesh="spear_blade_35"
length="41"
weight="0.3056"
excluded_item_usage_features="swing">
<BladeData
stack_amount="4"
physics_material="wood_weapon"
body_name="bo_spear_b"
holster_mesh="throwing_spear_quiver_5_1"
holster_body_name="bo_throwing_spear_quiver_5_1"
holster_mesh_length="96.7">
<Thrust
damage_type="Pierce"
damage_factor="2.0" />
</BladeData>
<Materials>
<Material
id="Iron3"
count="3" />
</Materials>
I believe the problem lies in the Flag <
name="NotStackable">. The Pilum has this flag and does not work, the JTS doesn't have it and works properly. Removing this flag from the Pilum Head and the Triangular Throwing Spear head seems to fix the bug. You can do that yourself, by going into crafting_piexes.xml.