セッション処理でエラー発生中

ブラウザによっては問題なく動作しています。あとで原因調査します。

Traceback (most recent call last):
File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/webapp/__init__.py", line 515, in __call__
handler.get(*groups)
File "/base/data/home/apps/rapidproxy/1.346766960722169101/main.py", line 34, in get
session = appengine_utilities.sessions.Session()
File "/base/data/home/apps/rapidproxy/1.346766960722169101/appengine_utilities/sessions.py", line 562, in __init__
self.session = _AppEngineUtilities_Session.get_session(self)
File "/base/data/home/apps/rapidproxy/1.346766960722169101/appengine_utilities/sessions.py", line 142, in get_session
ds_session = db.get(str(session_key))
File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/db/__init__.py", line 1318, in get
keys, multiple = datastore.NormalizeAndTypeCheckKeys(keys)
File "/base/python_runtime/python_lib/versions/1/google/appengine/api/datastore.py", line 144, in NormalizeAndTypeCheckKeys
keys = [_GetCompleteKeyOrError(key) for key in keys]
File "/base/python_runtime/python_lib/versions/1/google/appengine/api/datastore.py", line 2150, in _GetCompleteKeyOrError
key = Key(arg)
File "/base/python_runtime/python_lib/versions/1/google/appengine/api/datastore_types.py", line 304, in __init__
raise datastore_errors.BadKeyError('Invalid string key %s.' % encoded)
BadKeyError: Invalid string key agpyYXBpZHByb3h5ciQLEhtfQXBwRW5naW5lVXRpbGl0aWVzX1Nl********.