diff --git a/andes/core/model.py b/andes/core/model.py
index ed87a5be8..bcd02d20e 100644
--- a/andes/core/model.py
+++ b/andes/core/model.py
@@ -79,6 +79,9 @@ def refresh(self, name=None):
         ----------
         name : str, list, optional
             name or list of cached to refresh, by default None for refreshing all
+
+        TODO: bug found in Example notebook 2. Time domain initialization fails
+        after refreshing.
         """
         if name is None:
             for name in self._callbacks.keys():