diff --git a/lisa/conf.py b/lisa/conf.py
index 254f4471ebb6eeff3bc0aaabf717287f8c85cc15..685b7f933470df7b99abe2719183f63536525162 100644
--- a/lisa/conf.py
+++ b/lisa/conf.py
@@ -901,12 +901,22 @@ class MultiSrcConfABC(Serializable, abc.ABC):
                 return tuple(key1[:len_]) == tuple(key2[:len_])
 
             offending = [
-                cls_.__qualname__
+                cls_
                 for keys, cls_ in cls._REGISTERED_TOPLEVEL_KEYS.items()
                 if eq_prefix_keys(toplevel_keys, keys)
             ]
 
-            if offending:
+            # If the offending class has the same name and was declared in the
+            # same module, we ignore the conflict as this is probably arising
+            # from an import error in that module, that lead to the module
+            # being re-imported again (by another import statement).
+            if offending and not all(
+                (
+                    cls_.__qualname__ == cls.__qualname__ and
+                    cls_.__module__ == cls.__module__
+                )
+                for cls_ in offending
+            ):
                 raise RuntimeError(f'Class {cls.__qualname__} cannot reuse top level key "{format_keys(toplevel_keys)}" as it is already used by {", ".join(offending)}')
             else:
                 cls._REGISTERED_TOPLEVEL_KEYS[toplevel_keys] = cls
diff --git a/lisa/tests/base.py b/lisa/tests/base.py
index 5fe208eab21ef72e6693d58aa866b2492984d2ac..661e9d758fef9b62b88131e4766c0083f76896e1 100644
--- a/lisa/tests/base.py
+++ b/lisa/tests/base.py
@@ -1372,6 +1372,10 @@ class FtraceTestBundleBase(TestBundleBase):
             # iterations of the tests with exekall, leading to crashes.
             # Therefore, disable the on-disk swap.
             enable_swap=False,
+            # The event list that gets passed has already undergone namespace
+            # expansion when multiple ftrace conf got merged together, so there
+            # is no need to repeat it again.
+            events_namespaces=[],
         )
 
     def get_trace(self, events=None, **kwargs):
diff --git a/lisa/trace.py b/lisa/trace.py
index e52a518558ddcf39d9a190c0c5f897b45f7b5699..63e04e8f2a859c69271250d9c0dd5f5f5f547ff0 100644
--- a/lisa/trace.py
+++ b/lisa/trace.py
@@ -3702,7 +3702,7 @@ class Trace(Loggable, TraceBase):
         self.events = events
         # Pre-load the selected events
         if events:
-            preload_events = AndTraceEventChecker.from_events(
+            preload_events = OptionalTraceEventChecker.from_events(
                 event_
                 for event in events
                 for event_ in self._expand_namespaces(event, events_namespaces)
@@ -3738,24 +3738,25 @@ class Trace(Loggable, TraceBase):
         namespaces = self_or_cls._resolve_namespaces(namespaces)
 
         def expand(event, namespace):
-            if self_or_cls._is_meta_event(event):
+            ns_prefix = f'{namespace}__'
+            if not namespace:
+                return [event]
+            elif self_or_cls._is_meta_event(event):
                 prefix, _ = event.split('@', 1)
                 return [
                     f'{prefix}@{source_}'
                     for source in self_or_cls.get_event_sources(event)
                     for source_ in expand(source, namespace)
                 ]
+            elif event.startswith(ns_prefix):
+                return [event]
             else:
-                return [f'{namespace}__{event}']
+                return [f'{ns_prefix}{event}']
 
         return [
             event_
             for namespace in namespaces
-            for event_ in (
-                expand(event, namespace)
-                if namespace
-                else [event]
-            )
+            for event_ in expand(event, namespace)
         ]
 
     _CACHEABLE_METADATA = {