diff --git a/mindinsight/datavisual/data_transform/data_manager.py b/mindinsight/datavisual/data_transform/data_manager.py
index 1ec86bfe7cf6d1894b86a028cea39f58e19d553a..c63f8218141928d129fe9f66cde1084dd9981038 100644
--- a/mindinsight/datavisual/data_transform/data_manager.py
+++ b/mindinsight/datavisual/data_transform/data_manager.py
@@ -42,6 +42,7 @@ from mindinsight.datavisual.data_transform.loader_generators.loader_generator im
 from mindinsight.datavisual.data_transform.loader_generators.data_loader_generator import DataLoaderGenerator
 from mindinsight.utils.exceptions import MindInsightException
 from mindinsight.utils.exceptions import ParamValueError
+from mindinsight.utils.exceptions import UnknownError
 
 
 class _BasicTrainJob:
@@ -861,7 +862,7 @@ class DataManager:
         # Let gunicorn load other modules first.
         time.sleep(1)
         while True:
-            self._load_data_in_thread()
+            self._load_data_in_thread_wrapper()
 
             if not self._reload_interval:
                 break
@@ -874,18 +875,26 @@ class DataManager:
         This function needs to be used after `start_load_data` function.
         """
         logger.debug("start to reload data")
-        thread = threading.Thread(target=self._load_data_in_thread,
+        thread = threading.Thread(target=self._load_data_in_thread_wrapper,
                                   name='reload_data_thread')
         thread.daemon = False
         thread.start()
 
+    def _load_data_in_thread_wrapper(self):
+        """Wrapper for load data in thread."""
+        try:
+            self._load_data_in_thread()
+        except MindInsightException as exc:
+            # Not raising the exception here to ensure that data reloading does not crash.
+            logger.warning(exc.message)
+
     def _load_data_in_thread(self):
         """Log (but not swallow) exceptions in thread to help debugging."""
         try:
             self._load_data()
         except Exception as exc:
             logger.exception(exc)
-            raise
+            raise UnknownError('Load data thread error.')
 
     def _load_data(self):
         """This function will load data once and ignore it if the status is loading."""
diff --git a/mindinsight/datavisual/data_transform/summary_watcher.py b/mindinsight/datavisual/data_transform/summary_watcher.py
index e4b34a00143439f7fc2d5ee342aeaaaae275887d..e87d5374c8424294a701ccd3a5d6df56b3c9dd47 100644
--- a/mindinsight/datavisual/data_transform/summary_watcher.py
+++ b/mindinsight/datavisual/data_transform/summary_watcher.py
@@ -209,8 +209,14 @@ class SummaryWatcher:
                                 starting with "./" .
             entry (DirEntry): Directory entry instance needed to check with regular expression.
         """
-        ctime = datetime.datetime.fromtimestamp(entry.stat().st_ctime).astimezone()
-        mtime = datetime.datetime.fromtimestamp(entry.stat().st_mtime).astimezone()
+        try:
+            stat = entry.stat()
+        except FileNotFoundError:
+            logger.warning('File %s not found', entry.name)
+            return
+
+        ctime = datetime.datetime.fromtimestamp(stat.st_ctime).astimezone()
+        mtime = datetime.datetime.fromtimestamp(stat.st_mtime).astimezone()
 
         if entry.is_file():
             summary_pattern = re.search(self.SUMMARY_FILENAME_REGEX, entry.name)
@@ -304,7 +310,13 @@ class SummaryWatcher:
         return False
 
     def _is_empty_directory(self, directory):
-        return not bool(os.listdir(directory))
+        try:
+            count = len(os.listdir(directory))
+        except FileNotFoundError:
+            logger.warning('Directory %s not found.', directory)
+            count = 0
+
+        return not bool(count)
 
     def list_summary_directories_by_pagination(self, summary_base_dir, offset=0, limit=10):
         """
@@ -388,8 +400,13 @@ class SummaryWatcher:
             except OverflowError:
                 continue
 
-            # extract modified time from filesystem
-            mtime = datetime.datetime.fromtimestamp(entry.stat().st_mtime).astimezone()
+            try:
+                stat = entry.stat()
+            except FileNotFoundError:
+                logger.warning('File %s not found.', entry.name)
+                continue
+
+            mtime = datetime.datetime.fromtimestamp(stat.st_mtime).astimezone()
 
             summaries.append({
                 'file_name': entry.name,