fix for multi 2vs1 opponent sends out too many mons bug

src/battle_util.c

@@ -3816,6 +3816,21 @@ bool32 HasNoMonsToSwitch(u32 battler, u8 partyIdBattlerOn1, u8 partyIdBattlerOn2
         playerId = GetBattlerAtPosition(B_POSITION_OPPONENT_RIGHT);
         party = gEnemyParty;
 
+        // Edge case: If both opposing Pokemon were knocked out on the same turn,
+        // make sure opponent only sents out the final Pokemon once.
+        if (battler == playerId
+         && (gHitMarker & HITMARKER_FAINTED(flankId))
+         && (gHitMarker & HITMARKER_FAINTED(playerId)))
+        {
+            u8 count = 0;
+            for (i = 0; i < PARTY_SIZE; i++)
+                if (IsValidForBattle(&party[i]))
+                    count++;
+
+            if (count < 2)
+                return TRUE;
+        }
+
         if (partyIdBattlerOn1 == PARTY_SIZE)
             partyIdBattlerOn1 = gBattlerPartyIndexes[flankId];
         if (partyIdBattlerOn2 == PARTY_SIZE)