diff --git a/TM1py/Services/RestService.py b/TM1py/Services/RestService.py
index 6fbd0c51..20f29ae2 100644
--- a/TM1py/Services/RestService.py
+++ b/TM1py/Services/RestService.py
@@ -786,8 +786,22 @@ def _start_session(self, user: str, password: str, decode_b64: bool = False, nam
         finally:
             # If the TM1 REST API is routed through a reverse proxy that alters the expected URL,
             # we explicitly re-set the 'TM1SessionId' cookie to maintain session continuity.
-            session_id = self._s.cookies.pop('TM1SessionId', None)
-            if session_id is not None:
+            session_id = None
+            for cookie in self._s.cookies:
+                if cookie.name == 'TM1SessionId':
+                    session_id = cookie.value
+                    # break  # Use the first match
+
+            # Clear all TM1SessionId cookies to prevent duplicates
+            cookies_to_remove = [
+                (cookie.domain, cookie.path)
+                for cookie in self._s.cookies
+                if cookie.name == 'TM1SessionId'
+            ]
+            for domain, path in cookies_to_remove:
+                self._s.cookies.clear(domain=domain, path=path, name='TM1SessionId')
+
+            if session_id:
                 self._s.cookies.set('TM1SessionId', session_id)
 
             # After we have session cookie, drop the Authorization Header
diff --git a/TM1py/Utils/Utils.py b/TM1py/Utils/Utils.py
index 1cfea998..d6665b4a 100644
--- a/TM1py/Utils/Utils.py
+++ b/TM1py/Utils/Utils.py
@@ -545,7 +545,7 @@ def build_dataframe_from_csv(raw_csv, sep='~', shaped: bool = False,
 
     # make sure all element names are strings and values column is derived from data
     if 'dtype' not in kwargs:
-        kwargs['dtype'] = {'Value': None, **{col: str for col in range(999)}}
+        kwargs['dtype'] = {'Value': str, **{col: str for col in range(999)}}
     try:
         df = pd.read_csv(StringIO(raw_csv), sep=sep, na_values={'Value': ['None']}, keep_default_na=False, **kwargs)