diff --git a/x/stake/cross_stake/cross_stake.go b/x/stake/cross_stake/cross_stake.go
index 7ea761a6b..0965be6e9 100644
--- a/x/stake/cross_stake/cross_stake.go
+++ b/x/stake/cross_stake/cross_stake.go
@@ -127,6 +127,14 @@ func (app *CrossStakeApp) ExecuteFailAckPackage(ctx sdk.Context, payload []byte)
 			Recipient: p.Recipient,
 		}
 		result, err = app.handleDistributeUndelegatedRefund(ctx, refundPackage)
+	case *types.CrossStakeDistributeUndelegatedSynPackageV2:
+		bcAmount := bsc.ConvertBSCAmountToBCAmount(p.Amount)
+		refundPackage := &types.CrossStakeRefundPackage{
+			EventType: types.CrossStakeTypeDistributeUndelegated,
+			Amount:    big.NewInt(bcAmount),
+			Recipient: p.Recipient,
+		}
+		result, err = app.handleDistributeUndelegatedRefund(ctx, refundPackage)
 	default:
 		app.stakeKeeper.Logger(ctx).Error("unknown cross stake fail ack event type", "err", err.Error(), "package", string(payload))
 		return sdk.ExecuteResult{}
diff --git a/x/stake/cross_stake/serialize.go b/x/stake/cross_stake/serialize.go
index 8cb9a8be5..8c4bdb8e6 100644
--- a/x/stake/cross_stake/serialize.go
+++ b/x/stake/cross_stake/serialize.go
@@ -84,6 +84,17 @@ func DeserializeCrossStakeFailAckPackage(serializedPackage []byte) (interface{},
 			}
 			return &pack, nil
 		},
+		func(serializedPackage []byte) (interface{}, error) {
+			var pack types.CrossStakeDistributeUndelegatedSynPackageV2
+			err := rlp.DecodeBytes(serializedPackage, &pack)
+			if err != nil {
+				return nil, err
+			}
+			if pack.EventType != types.CrossStakeTypeDistributeUndelegated {
+				return nil, fmt.Errorf("wrong cross stake event type")
+			}
+			return &pack, nil
+		},
 	}
 
 	var pack interface{}
diff --git a/x/stake/endblock.go b/x/stake/endblock.go
index c0342311d..86a7a677e 100644
--- a/x/stake/endblock.go
+++ b/x/stake/endblock.go
@@ -279,7 +279,8 @@ func handleMatureUnbondingDelegations(k keeper.Keeper, ctx sdk.Context) ([]types
 }
 
 const (
-	maxProcessedRefundCount = 10
+	maxProcessedRefundCount  = 10
+	maxProcessedRefundFailed = 200
 )
 
 func handleRefundStake(ctx sdk.Context, sideChainPrefix []byte, k keeper.Keeper) sdk.Events {
@@ -287,7 +288,8 @@ func handleRefundStake(ctx sdk.Context, sideChainPrefix []byte, k keeper.Keeper)
 	iterator := k.IteratorAllDelegations(sideChainCtx)
 	defer iterator.Close()
 	var refundEvents sdk.Events
-	count := 0
+	succeedCount := 0
+	failedCount := 0
 	boundDenom := k.BondDenom(sideChainCtx)
 	bscSideChainId := k.ScKeeper.BscSideChainId(ctx)
 
@@ -304,6 +306,27 @@ func handleRefundStake(ctx sdk.Context, sideChainPrefix []byte, k keeper.Keeper)
 			SideChainId:   bscSideChainId,
 		}, k)
 		refundEvents = refundEvents.AppendEvents(result.Events)
+		if !result.IsOK() {
+			ctx.Logger().Debug("handleRefundStake failed",
+				"delegator", delegation.DelegatorAddr.String(),
+				"validator", delegation.ValidatorAddr.String(),
+				"amount", delegation.GetShares().String(),
+				"sideChainId", bscSideChainId,
+				"result", fmt.Sprintf("%+v", result),
+			)
+			// this is to prevent too many delegation is in unbounded state
+			// if too many delegation is in unbounded state, it will cause too many iteration in the block
+			failedCount++
+			if failedCount >= maxProcessedRefundFailed {
+				break
+			}
+
+			continue
+		}
+
+		if result.IsOK() && delegation.CrossStake {
+			k.SetAutoUnDelegate(sideChainCtx, delegation.DelegatorAddr, delegation.ValidatorAddr)
+		}
 
 		ctx.Logger().Info("handleRefundStake after SecondSunsetFork",
 			"delegator", delegation.DelegatorAddr.String(),
@@ -311,8 +334,8 @@ func handleRefundStake(ctx sdk.Context, sideChainPrefix []byte, k keeper.Keeper)
 			"amount", delegation.GetShares().String(),
 			"sideChainId", bscSideChainId,
 		)
-		count++
-		if count >= maxProcessedRefundCount {
+		succeedCount++
+		if succeedCount >= maxProcessedRefundCount {
 			break
 		}
 	}
diff --git a/x/stake/handler.go b/x/stake/handler.go
index cebd507d6..379b7c101 100644
--- a/x/stake/handler.go
+++ b/x/stake/handler.go
@@ -70,6 +70,9 @@ func NewHandler(k keeper.Keeper, govKeeper gov.Keeper) sdk.Handler {
 			}
 			return handleMsgSideChainRedelegate(ctx, msg, k)
 		case types.MsgSideChainUndelegate:
+			if sdk.IsUpgrade(sdk.SecondSunsetFork) {
+				return sdk.ErrMsgNotSupported("").Result()
+			}
 			return handleMsgSideChainUndelegate(ctx, msg, k)
 		case types.MsgSideChainStakeMigration:
 			if !sdk.IsUpgrade(sdk.FirstSunsetFork) || sdk.IsUpgrade(sdk.SecondSunsetFork) {
diff --git a/x/stake/keeper/delegation.go b/x/stake/keeper/delegation.go
index 5a210491d..b4c1c66f2 100644
--- a/x/stake/keeper/delegation.go
+++ b/x/stake/keeper/delegation.go
@@ -739,6 +739,20 @@ func (k Keeper) CompleteUnbonding(ctx sdk.Context, delAddr sdk.AccAddress, valAd
 	return ubd, events, nil
 }
 
+func (k Keeper) IsAutoUnDelegate(ctx sdk.Context, delAddr sdk.AccAddress, valAddr sdk.ValAddress) bool {
+	store := ctx.KVStore(k.storeKey)
+	key := GetAutoUnDelegateIndexKey(delAddr, valAddr)
+
+	return store.Has(key)
+}
+
+func (k Keeper) SetAutoUnDelegate(ctx sdk.Context, delAddr sdk.AccAddress, valAddr sdk.ValAddress) {
+	store := ctx.KVStore(k.storeKey)
+
+	key := GetAutoUnDelegateIndexKey(delAddr, valAddr)
+	store.Set(key, []byte{}) // index, store empty bytes
+}
+
 // complete unbonding an unbonding record
 func (k Keeper) BeginRedelegation(ctx sdk.Context, delAddr sdk.AccAddress,
 	valSrcAddr, valDstAddr sdk.ValAddress, sharesAmount sdk.Dec) (types.Redelegation, sdk.Error) {
@@ -875,12 +889,24 @@ func (k Keeper) crossDistributeUndelegated(ctx sdk.Context, delAddr sdk.AccAddre
 		return sdk.Events{}, sdk.ErrInternal(err.Error())
 	}
 
-	transferPackage := types.CrossStakeDistributeUndelegatedSynPackage{
-		EventType: types.CrossStakeTypeDistributeUndelegated,
-		Amount:    bscTransferAmount,
-		Recipient: recipient,
-		Validator: valAddr,
+	var transferPackage interface{}
+	if !sdk.IsUpgrade(sdk.SecondSunsetFork) {
+		transferPackage = types.CrossStakeDistributeUndelegatedSynPackage{
+			EventType: types.CrossStakeTypeDistributeUndelegated,
+			Amount:    bscTransferAmount,
+			Recipient: recipient,
+			Validator: valAddr,
+		}
+	} else {
+		transferPackage = types.CrossStakeDistributeUndelegatedSynPackageV2{
+			EventType:        types.CrossStakeTypeDistributeUndelegated,
+			Amount:           bscTransferAmount,
+			Recipient:        recipient,
+			Validator:        valAddr,
+			IsAutoUnDelegate: k.IsAutoUnDelegate(ctx, delAddr, valAddr),
+		}
 	}
+
 	encodedPackage, err := rlp.EncodeToBytes(transferPackage)
 	if err != nil {
 		return sdk.Events{}, sdk.ErrInternal(err.Error())
diff --git a/x/stake/keeper/key.go b/x/stake/keeper/key.go
index e76bcb124..288c62441 100644
--- a/x/stake/keeper/key.go
+++ b/x/stake/keeper/key.go
@@ -50,6 +50,8 @@ var (
 	// Keys for reward store prefix
 	RewardBatchKey       = []byte{0x01} // key for batch of rewards
 	RewardValDistAddrKey = []byte{0x02} // key for rewards' validator <-> distribution address mapping
+
+	AutoUndelegateIndexKey = []byte{0x61} // prefix for each key for an auto undelegate, by validator operator
 )
 
 const (
@@ -340,3 +342,14 @@ func GetREDsByDelToValDstIndexKey(delAddr sdk.AccAddress, valDstAddr sdk.ValAddr
 func GetValLatestUpdateConsAddrTimeKey(valAddr sdk.ValAddress) []byte {
 	return append(ValLatestUpdateConsAddrTimeKey, valAddr.Bytes()...)
 }
+
+// gets the prefix keyspace for the indexes of auto unDelegate delegations for a validator
+func GetAutoUnDelegateByValIndexKey(valAddr sdk.ValAddress) []byte {
+	return append(AutoUndelegateIndexKey, valAddr.Bytes()...)
+}
+
+// gets the index-key for an auto unDelegate delegation, stored by validator-index
+// VALUE: none (key rearrangement used)
+func GetAutoUnDelegateIndexKey(delAddr sdk.AccAddress, valAddr sdk.ValAddress) []byte {
+	return append(GetAutoUnDelegateByValIndexKey(valAddr), delAddr.Bytes()...)
+}
diff --git a/x/stake/types/cross_stake.go b/x/stake/types/cross_stake.go
index 6cc2d406d..74d9c76cb 100644
--- a/x/stake/types/cross_stake.go
+++ b/x/stake/types/cross_stake.go
@@ -80,6 +80,14 @@ type CrossStakeDistributeUndelegatedSynPackage struct {
 	Amount    *big.Int
 }
 
+type CrossStakeDistributeUndelegatedSynPackageV2 struct {
+	EventType        CrossStakeEventType
+	Recipient        sdk.SmartChainAddress
+	Validator        sdk.ValAddress
+	Amount           *big.Int
+	IsAutoUnDelegate bool
+}
+
 type RefundError uint32
 
 const (