diff --git a/src/connector/src/parser/unified/debezium.rs b/src/connector/src/parser/unified/debezium.rs
index 067324ec01980..5a54a550e816d 100644
--- a/src/connector/src/parser/unified/debezium.rs
+++ b/src/connector/src/parser/unified/debezium.rs
@@ -257,10 +257,11 @@ where
                         &bson_doc.take(),
                     )?)
                 } else {
-                    unreachable!(
-                        "access result must match the type_expected. path: {:?}, payload: {:?}, type_expected: {:?}",
-                        path, payload, type_expected
-                    )
+                    // fail to extract the "_id" field from the message payload
+                    Err(AccessError::Undefined {
+                        name: "_id".to_string(),
+                        path: path[0].to_string(),
+                    })
                 }
             }
             ["after" | "before", "payload"] => self.access(&[path[0]], Some(&DataType::Jsonb)),
@@ -277,10 +278,11 @@ where
                             &bson_doc.take(),
                         )?)
                     } else {
-                        unreachable!(
-                            "access result must match the type_expected. path: [\"id\"], id: {:?}, type_expected: {:?}",
-                            id_bson, type_expected
-                        )
+                        // fail to extract the "_id" field from the message key
+                        Err(AccessError::Undefined {
+                            name: "_id".to_string(),
+                            path: "id".to_string(),
+                        })
                     }
                 } else {
                     ret
diff --git a/src/connector/src/source/cdc/split.rs b/src/connector/src/source/cdc/split.rs
index 27a39946c015b..0fa639ebbaebe 100644
--- a/src/connector/src/source/cdc/split.rs
+++ b/src/connector/src/source/cdc/split.rs
@@ -196,14 +196,13 @@ impl CdcSplitTrait for MongoDbCdcSplit {
         let mut snapshot_done = self.inner.snapshot_done;
         // extract snapshot state from debezium offset
         if !snapshot_done {
-            let dbz_offset: DebeziumOffset = serde_json::from_str(&start_offset).map_err(|e| {
-                anyhow!(
-                    "invalid mongodb offset: {}, error: {}, split: {}",
-                    start_offset,
-                    e,
-                    self.inner.split_id
-                )
-            })?;
+            let dbz_offset: DebeziumOffset =
+                serde_json::from_str(&start_offset).with_context(|| {
+                    format!(
+                        "invalid mongodb offset: {}, split: {}",
+                        start_offset, self.inner.split_id
+                    )
+                })?;
 
             // heartbeat event should not update the `snapshot_done` flag
             if !dbz_offset.is_heartbeat {
@@ -235,7 +234,7 @@ pub struct DebeziumCdcSplit<T: CdcSourceTypeTrait> {
     pub _phantom: PhantomData<T>,
 }
 
-macro_rules! dispatch_cdc_split {
+macro_rules! dispatch_cdc_split_inner {
     ($dbz_split:expr, $as_type:tt, {$($cdc_source_type:tt),*}, $body:expr) => {
         match T::source_type() {
             $(
@@ -255,6 +254,13 @@ macro_rules! dispatch_cdc_split {
     }
 }
 
+// call corresponding split method of the specific cdc source type
+macro_rules! dispatch_cdc_split {
+    ($dbz_split:expr, $as_type:tt, $body:expr) => {
+      dispatch_cdc_split_inner!($dbz_split, $as_type, {Mysql, Postgres, Citus, Mongodb}, $body)
+    }
+}
+
 impl<T: CdcSourceTypeTrait> SplitMetaData for DebeziumCdcSplit<T> {
     fn id(&self) -> SplitId {
         format!("{}", self.split_id()).into()
@@ -307,39 +313,19 @@ impl<T: CdcSourceTypeTrait> DebeziumCdcSplit<T> {
     }
 
     pub fn split_id(&self) -> u32 {
-        dispatch_cdc_split!(self, ref, {
-            Mysql,
-            Postgres,
-            Citus,
-            Mongodb
-        }, split_id())
+        dispatch_cdc_split!(self, ref, split_id())
     }
 
     pub fn start_offset(&self) -> &Option<String> {
-        dispatch_cdc_split!(self, ref, {
-            Mysql,
-            Postgres,
-            Citus,
-            Mongodb
-        }, start_offset())
+        dispatch_cdc_split!(self, ref, start_offset())
     }
 
     pub fn snapshot_done(&self) -> bool {
-        dispatch_cdc_split!(self, ref, {
-            Mysql,
-            Postgres,
-            Citus,
-            Mongodb
-        }, is_snapshot_done())
+        dispatch_cdc_split!(self, ref, is_snapshot_done())
     }
 
     pub fn update_with_offset(&mut self, start_offset: String) -> anyhow::Result<()> {
-        dispatch_cdc_split!(self, mut, {
-            Mysql,
-            Postgres,
-            Citus,
-            Mongodb
-        }, update_with_offset(start_offset)?);
+        dispatch_cdc_split!(self, mut, update_with_offset(start_offset)?);
         Ok(())
     }
 }