diff --git a/pandas/core/groupby/generic.py b/pandas/core/groupby/generic.py
index 9d6d2d698dfe5..eac2cdb9dcd0f 100644
--- a/pandas/core/groupby/generic.py
+++ b/pandas/core/groupby/generic.py
@@ -275,7 +275,7 @@ def aggregate(self, func=None, *args, engine=None, engine_kwargs=None, **kwargs)
 
             try:
                 return self._python_agg_general(func, *args, **kwargs)
-            except (ValueError, KeyError):
+            except KeyError:
                 # TODO: KeyError is raised in _python_agg_general,
                 #  see test_groupby.test_basic
                 result = self._aggregate_named(func, *args, **kwargs)
@@ -594,6 +594,7 @@ def _transform_general(self, func, *args, **kwargs):
 
         results = []
         for name, group in self:
+            # this setattr is needed for test_transform_lambda_with_datetimetz
             object.__setattr__(group, "name", name)
             res = func(group, *args, **kwargs)
 
diff --git a/pandas/core/groupby/ops.py b/pandas/core/groupby/ops.py
index 3ee185d862b01..d0fb100fdbd9f 100644
--- a/pandas/core/groupby/ops.py
+++ b/pandas/core/groupby/ops.py
@@ -1089,6 +1089,9 @@ def agg_series(self, obj: Series, func: F):
             # preempt SeriesBinGrouper from raising TypeError
             return self._aggregate_series_pure_python(obj, func)
 
+        elif obj.index._has_complex_internals:
+            return self._aggregate_series_pure_python(obj, func)
+
         grouper = libreduction.SeriesBinGrouper(obj, func, self.bins)
         return grouper.get_result()