diff --git a/backend/MediaCacheManager.py b/backend/MediaCacheManager.py
index 00e3aa4..1e9f1a0 100644
--- a/backend/MediaCacheManager.py
+++ b/backend/MediaCacheManager.py
@@ -42,8 +42,8 @@ class ChunkInfo(object):
 @functools.total_ordering
 class MediaChunkHolder(object):
     waiters: collections.deque[asyncio.Future]
-    requesters: list[Request] = []
-    unique_id: str = ""
+    requesters: list[Request]
+    unique_id: str
     info: ChunkInfo
 
     @staticmethod
@@ -56,9 +56,11 @@ class MediaChunkHolder(object):
         self.mem = bytes()
         self.length = len(self.mem)
         self.waiters = collections.deque()
+        self.requesters = []
 
     def __repr__(self) -> str:
-        return f"MediaChunk,unique_id:{self.unique_id},{self.info},mlen:{self.length}"
+        pl = [f"{id(req)}" for req in self.requesters]
+        return f"MediaChunk,unique_id:{self.unique_id},{self.info},mlen:{self.length},req:{pl}"
 
     def __eq__(self, other: Union["MediaChunkHolder", ChunkInfo, int]):
         if isinstance(other, int):
@@ -110,11 +112,12 @@ class MediaChunkHolder(object):
 
     async def is_disconneted(self) -> bool:
         while self.requesters:
-            req = self.requesters[0]
-            if not await req.is_disconnected():
-                return False
             try:
+                req = self.requesters[0]
+                if not await req.is_disconnected():
+                    return False
                 self.requesters.remove(req)
+                logger.info(f"remove req:{id(req)=},{self}")
             except Exception as err:
                 logger.warning(f"{err=}, trace:{traceback.format_exc()}")
                 return False
@@ -127,9 +130,9 @@ class MediaChunkHolder(object):
         self.waiters.append(waiter)
         try:
             await waiter
-        except:
+        except Exception as err:
             waiter.cancel()
-            logger.warning("waiter cancel")
+            logger.warning(f"waiter cancel:{err=},{traceback.format_exc()}")
             try:
                 self.waiters.remove(waiter)
             except ValueError:
diff --git a/backend/TgFileSystemClient.py b/backend/TgFileSystemClient.py
index 22645d4..802a9b6 100644
--- a/backend/TgFileSystemClient.py
+++ b/backend/TgFileSystemClient.py
@@ -356,6 +356,7 @@ class TgFileSystemClient(object):
                     align_pos = pos
                     align_size = min(self.SINGLE_MEDIA_SIZE, file_size - align_pos)
                     holder = self.media_chunk_manager.create_media_chunk_holder(msg.chat_id, msg.id, align_pos, align_size)
+                    logger.info(f"new holder create:{holder}")
                     holder.add_chunk_requester(req)
                     self.media_chunk_manager.set_media_chunk(holder)
                     self.task_queue.put_nowait((cur_task_id, self._download_media_chunk(msg, holder)))
diff --git a/backend/api.py b/backend/api.py
index e29c1fd..b17c879 100644
--- a/backend/api.py
+++ b/backend/api.py
@@ -177,7 +177,6 @@ async def get_tg_file_media_stream(token: str, cid: int, mid: int, request: Requ
 @app.get("/tg/api/v1/file/get/{chat_id}/{msg_id}/{file_name}")
 @apiutils.atimeit
 async def get_tg_file_media(chat_id: int|str, msg_id: int, file_name: str, sign: str, req: Request):
-    logger.info(f"request: {chat_id=},{msg_id=},{file_name=},{req=},{id(req)=}")
     try:
         if isinstance(chat_id, str):
             chat_id = int(chat_id)
diff --git a/frontend/home.py b/frontend/home.py
index 3004f28..feec3f5 100644
--- a/frontend/home.py
+++ b/frontend/home.py
@@ -9,7 +9,7 @@ st.set_page_config(page_title="TgToolbox", page_icon="🕹️", layout="wide", i
 backend_status = api.get_backend_client_status()
 need_login = False
 
-if not backend_status["init"]:
+if backend_status is None or not backend_status["init"]:
     st.status("Server not ready")
     time.sleep(0.5)
     st.rerun()