i believe thats usually caused by a problem in the PromotionInfos XML file. usually something very simple, like putting
<Type>PROMOTION_COMBAT_5</Type>
instead of
<Type>PROMOTION_COMBAT5</Type>
which throw it out completely,
or accidentally adding an extra line of text like
<UnitCombat>
<UnitCombatType>UNITCOMBAT_MOUNTED</UnitCombatType>
<bUnitCombat>1</bUnitCombat>
</UnitCombat>
</UnitCombat>
<UnitCombat>
<UnitCombatType>UNITCOMBAT_NAVAL</UnitCombatType>
<bUnitCombat>1</bUnitCombat>
</UnitCombat>
or removing a line of text like
<bLeader>0</bLeader>
<bBlitz>0</bBlitz>
<bAmphib>0</bAmphib>
<bEnemyRoute>0</bEnemyRoute>
instead of
<bLeader>0</bLeader>
<bBlitz>0</bBlitz>
<bAmphib>0</bAmphib>
<bRiver>0</bRiver>
<bEnemyRoute>0</bEnemyRoute>
i may be wrong because im a noob at this whole modding thing, but thats whats caused that problem for me in the past
