diff --git a/api/db/services/task_service.py b/api/db/services/task_service.py
index 5fd0eefc3..1fdfed350 100644
--- a/api/db/services/task_service.py
+++ b/api/db/services/task_service.py
@@ -387,12 +387,12 @@ def queue_tasks(doc: dict, bucket: str, name: str, priority: int):
         for task in parse_task_array:
             ck_num += reuse_prev_task_chunks(task, prev_tasks, chunking_config)
         TaskService.filter_delete([Task.doc_id == doc["id"]])
-        chunk_ids = []
-        for task in prev_tasks:
-            if task["chunk_ids"]:
-                chunk_ids.extend(task["chunk_ids"].split())
-        if chunk_ids:
-            settings.docStoreConn.delete({"id": chunk_ids}, search.index_name(chunking_config["tenant_id"]),
+        pre_chunk_ids = []
+        for pre_task in prev_tasks:
+            if pre_task["chunk_ids"]:
+                pre_chunk_ids.extend(pre_task["chunk_ids"].split())
+        if pre_chunk_ids:
+            settings.docStoreConn.delete({"id": pre_chunk_ids}, search.index_name(chunking_config["tenant_id"]),
                                          chunking_config["kb_id"])
     DocumentService.update_by_id(doc["id"], {"chunk_num": ck_num})
 
diff --git a/rag/svr/task_executor.py b/rag/svr/task_executor.py
index b028f7125..0377c72c3 100644
--- a/rag/svr/task_executor.py
+++ b/rag/svr/task_executor.py
@@ -543,6 +543,7 @@ async def do_handle_task(task):
     # Either using graphrag or Standard chunking methods
     elif task.get("task_type", "") == "graphrag":
         if not task_parser_config.get("graphrag", {}).get("use_graphrag", False):
+            progress_callback(prog=-1.0, msg="Internal configuration error.")
             return
         graphrag_conf = task["kb_parser_config"].get("graphrag", {})
         start_ts = timer()
@@ -558,8 +559,6 @@ async def do_handle_task(task):
         start_ts = timer()
         chunks = await build_chunks(task, progress_callback)
         logging.info("Build document {}: {:.2f}s".format(task_document_name, timer() - start_ts))
-        if chunks is None:
-            return
         if not chunks:
             progress_callback(1., msg=f"No chunk built from {task_document_name}")
             return
@@ -614,6 +613,7 @@ async def do_handle_task(task):
             async with trio.open_nursery() as nursery:
                 for chunk_id in chunk_ids:
                     nursery.start_soon(delete_image, task_dataset_id, chunk_id)
+            progress_callback(-1, msg=f"Chunk updates failed since task {task['id']} is unknown.")
             return
         
     logging.info("Indexing doc({}), page({}-{}), chunks({}), elapsed: {:.2f}".format(task_document_name, task_from_page,