diff --git a/dm/worker/task_checker.go b/dm/worker/task_checker.go
index 8589e17cd4..d5fa5f0ae1 100644
--- a/dm/worker/task_checker.go
+++ b/dm/worker/task_checker.go
@@ -259,21 +259,25 @@ func (tsc *realTaskStatusChecker) run() {
 // isResumableError checks the error message and returns whether we need to
 // resume the task and retry
 func isResumableError(err *pb.ProcessError) bool {
+	if err.Error == nil {
+		return true
+	}
+
 	switch err.Type {
 	case pb.ErrorType_ExecSQL:
 		// not elegant code, because TiDB doesn't expose some error
 		for _, msg := range retry.UnsupportedDDLMsgs {
-			if err.Error != nil && strings.Contains(strings.ToLower(err.Error.RawCause), strings.ToLower(msg)) {
+			if strings.Contains(strings.ToLower(err.Error.RawCause), strings.ToLower(msg)) {
 				return false
 			}
 		}
 		for _, msg := range retry.UnsupportedDMLMsgs {
-			if err.Error != nil && strings.Contains(strings.ToLower(err.Error.RawCause), strings.ToLower(msg)) {
+			if strings.Contains(strings.ToLower(err.Error.RawCause), strings.ToLower(msg)) {
 				return false
 			}
 		}
 	case pb.ErrorType_UnknownError:
-		if err.Error != nil && err.Error.ErrCode == int32(terror.ErrParserParseRelayLog.Code()) {
+		if err.Error.ErrCode == int32(terror.ErrParserParseRelayLog.Code()) {
 			for _, msg := range retry.ParseRelayLogErrMsgs {
 				if strings.Contains(strings.ToLower(err.Error.Message), strings.ToLower(msg)) {
 					return false
@@ -282,6 +286,10 @@ func isResumableError(err *pb.ProcessError) bool {
 		}
 	}
 
+	if _, ok := retry.UnresumableErrCodes[err.Error.ErrCode]; ok {
+		return false
+	}
+
 	return true
 }
 
diff --git a/dm/worker/worker.go b/dm/worker/worker.go
index 1a70b6efb6..5525d86798 100644
--- a/dm/worker/worker.go
+++ b/dm/worker/worker.go
@@ -741,6 +741,9 @@ func (w *Worker) restoreSubTask() error {
 			return terror.Annotatef(err, "decode subtask config %s error in restoreSubTask", task.Task)
 		}
 
+		// when restarting DM-worker, some config items may need to be updated for the previous saved task config.
+		w.copyConfigFromWorker(taskCfg)
+
 		cfgDecrypted, err := taskCfg.DecryptPassword()
 		if err != nil {
 			return err
diff --git a/pkg/retry/errors.go b/pkg/retry/errors.go
index a04fb730a3..2a2e0bc713 100644
--- a/pkg/retry/errors.go
+++ b/pkg/retry/errors.go
@@ -15,6 +15,8 @@ package retry
 
 import (
 	"database/sql/driver"
+
+	"github.com/pingcap/dm/pkg/terror"
 	"github.com/pingcap/errors"
 )
 
@@ -41,6 +43,11 @@ var (
 		"binlog checksum mismatch, data may be corrupted",
 		"get event err EOF",
 	}
+
+	// UnresumableErrCodes is a set of unresumeable err codes.
+	UnresumableErrCodes = map[int32]struct{}{
+		int32(terror.ErrSyncUnitDDLWrongSequence.Code()): {},
+	}
 )
 
 // IsConnectionError tells whether this error should reconnect to Database
diff --git a/syncer/sharding-meta/shardmeta.go b/syncer/sharding-meta/shardmeta.go
index ea8395a730..536a3b5f5c 100644
--- a/syncer/sharding-meta/shardmeta.go
+++ b/syncer/sharding-meta/shardmeta.go
@@ -120,7 +120,8 @@ func (meta *ShardingMeta) ActiveIdx() int {
 	return meta.activeIdx
 }
 
-func (meta *ShardingMeta) reinitialize() {
+// Reinitialize reinitialize the shardingmeta
+func (meta *ShardingMeta) Reinitialize() {
 	meta.activeIdx = 0
 	meta.global = &ShardingSequence{make([]*DDLItem, 0)}
 	meta.sources = make(map[string]*ShardingSequence)
@@ -220,7 +221,7 @@ func (meta *ShardingMeta) InSequenceSharding() bool {
 func (meta *ShardingMeta) ResolveShardingDDL() bool {
 	meta.activeIdx++
 	if meta.activeIdx == len(meta.global.Items) {
-		meta.reinitialize()
+		meta.Reinitialize()
 		return true
 	}
 	return false
diff --git a/syncer/sharding_group.go b/syncer/sharding_group.go
index 0f4f1281a7..2a4e1d3e78 100644
--- a/syncer/sharding_group.go
+++ b/syncer/sharding_group.go
@@ -480,6 +480,9 @@ func (k *ShardingGroupKeeper) ResetGroups() {
 	defer k.RUnlock()
 	for _, group := range k.groups {
 		group.Reset()
+		// reset ShardingMeta when start or resume task
+		// it will be reconstructed by consuming binlog event
+		group.meta.Reinitialize()
 	}
 }
 
diff --git a/tests/sequence_sharding/data/db1.increment3.sql b/tests/sequence_sharding/data/db1.increment3.sql
new file mode 100644
index 0000000000..9d66b64a8c
--- /dev/null
+++ b/tests/sequence_sharding/data/db1.increment3.sql
@@ -0,0 +1,5 @@
+use sharding_seq;
+alter table t1 add column new_col1 int;
+alter table t1 add column new_col2 int;
+alter table t2 add column new_col1 int;
+alter table t2 add column new_col3 int;
diff --git a/tests/sequence_sharding/data/db2.increment3.sql b/tests/sequence_sharding/data/db2.increment3.sql
new file mode 100644
index 0000000000..f366aecab3
--- /dev/null
+++ b/tests/sequence_sharding/data/db2.increment3.sql
@@ -0,0 +1,7 @@
+use sharding_seq;
+alter table t2 add column new_col1 int;
+alter table t2 add column new_col2 int;
+alter table t3 add column new_col1 int;
+alter table t3 add column new_col2 int;
+alter table t4 add column new_col1 int;
+alter table t4 add column new_col3 int;
diff --git a/tests/sequence_sharding/run.sh b/tests/sequence_sharding/run.sh
index 6fb5982b26..cf87cedc5c 100755
--- a/tests/sequence_sharding/run.sh
+++ b/tests/sequence_sharding/run.sh
@@ -62,6 +62,46 @@ function run() {
         "query-status sequence_sharding" \
         "\"stage\": \"Running\"" 4 \
         "\"unit\": \"Sync\"" 2
+
+
+    run_sql_file $cur/data/db1.increment3.sql $MYSQL_HOST1 $MYSQL_PORT1 $MYSQL_PASSWORD1
+    run_sql_file $cur/data/db2.increment3.sql $MYSQL_HOST2 $MYSQL_PORT2 $MYSQL_PASSWORD2
+
+    sleep 2
+
+    # the first ddl success while the second is conflict
+    run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
+        "query-status sequence_sharding" \
+        "detect inconsistent DDL sequence" 2
+    
+    run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
+        "resume-task sequence_sharding" \
+        "\"result\": true" 3
+
+    sleep 2
+
+    # still conflict
+    run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
+        "query-status sequence_sharding" \
+        "detect inconsistent DDL sequence" 2
+
+    run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
+        "stop-task sequence_sharding" \
+        "\"result\": true" 3
+    
+    # now upstream schema is conflict, ignore it and restart task
+    cp $cur/conf/dm-task.yaml $WORK_DIR/task.yaml
+    echo "ignore-checking-items: [\"all\"]" >> $WORK_DIR/task.yaml
+    run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
+        "start-task $WORK_DIR/task.yaml" \
+        "\"result\": true" 3
+    
+    sleep 2
+
+    # still conflict
+    run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
+        "query-status sequence_sharding" \
+        "detect inconsistent DDL sequence" 2
 }
 
 cleanup_data sharding_target2
diff --git a/tests/sharding/run.sh b/tests/sharding/run.sh
index 2a5ee8a06b..2a8266d604 100755
--- a/tests/sharding/run.sh
+++ b/tests/sharding/run.sh
@@ -64,6 +64,33 @@ function run() {
     new_checksum=$(checksum)
     echo "checksum before drop/truncate: $old_checksum, checksum after drop/truncate: $new_checksum"
     [ "$old_checksum" == "$new_checksum" ]
+
+    # test conflict ddl in single worker
+    run_sql "alter table sharding1.t1 add column new_col1 int;" $MYSQL_PORT1 $MYSQL_PASSWORD1
+    run_sql "alter table sharding1.t2 add column new_col2 int;" $MYSQL_PORT1 $MYSQL_PASSWORD1
+
+    sleep 2
+
+    run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
+        "query-status test" \
+        "detect inconsistent DDL sequence" 1
+
+
+    run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
+        "resume-task test -w 127.0.0.1:8262"\
+        "\"result\": true" 2
+
+    sleep 2
+
+    # still conflict
+    run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
+        "query-status test" \
+        "detect inconsistent DDL sequence" 1
+
+    # stop twice, just used to test stop by the way
+    run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
+        "stop-task test"\
+        "\"result\": true" 3
 }
 
 cleanup_data db_target