Core/Spell: Fixed bug where spell could fail to hit a target properly even if all conditions were met (#18596)

src/server/game/Spells/Spell.cpp

@@ -3069,7 +3069,11 @@ void Spell::prepare(SpellCastTargets const* targets, AuraEffect const* triggered
             TriggerGlobalCooldown();
 
         //item: first cast may destroy item and second cast causes crash
-        if (!m_casttime && !m_spellInfo->StartRecoveryTime && !m_castItemGUID && GetCurrentContainer() == CURRENT_GENERIC_SPELL)
+        // commented out !m_spellInfo->StartRecoveryTime, it forces instant spells with global cooldown to be processed in spell::update
+        // as a result a spell that passed CheckCast and should be processed instantly may suffer from this delayed process
+        // the easiest bug to observe is LoS check in AddUnitTarget, even if spell passed the CheckCast LoS check the situation can change in spell::update
+        // because target could be relocated in the meantime, making the spell fly to the air (no targets can be registered, so no effects processed, nothing in combat log)
+        if (!m_casttime && /*!m_spellInfo->StartRecoveryTime && */!m_castItemGUID && GetCurrentContainer() == CURRENT_GENERIC_SPELL)
             cast(true);
     }
 }