diff --git a/frigate/test/test_stationary_classifier.py b/frigate/test/test_stationary_classifier.py
new file mode 100644
index 0000000000..bd5e2c41e2
--- /dev/null
+++ b/frigate/test/test_stationary_classifier.py
@@ -0,0 +1,39 @@
+"""Tests for stationary object classification thresholds."""
+
+import unittest
+
+from frigate.track.stationary_classifier import (
+    DEFAULT_OBJECT_THRESHOLDS,
+    DYNAMIC_OBJECT_THRESHOLDS,
+    NON_STATIONARY_OBJECT_THRESHOLDS,
+    STATIONARY_OBJECT_THRESHOLDS,
+    StationaryThresholds,
+    get_stationary_threshold,
+)
+
+
+class TestStationaryThresholds(unittest.TestCase):
+    def test_known_labels_return_expected_singletons(self) -> None:
+        self.assertIs(get_stationary_threshold("package"), STATIONARY_OBJECT_THRESHOLDS)
+        self.assertIs(get_stationary_threshold("car"), DYNAMIC_OBJECT_THRESHOLDS)
+        self.assertIs(
+            get_stationary_threshold("license_plate"),
+            NON_STATIONARY_OBJECT_THRESHOLDS,
+        )
+
+    def test_unknown_label_returns_shared_default(self) -> None:
+        # an unknown label must reuse the shared default instance, not allocate
+        # a fresh one on every call (this runs per object per frame)
+        first = get_stationary_threshold("person")
+        second = get_stationary_threshold("dog")
+        self.assertIs(first, DEFAULT_OBJECT_THRESHOLDS)
+        self.assertIs(second, DEFAULT_OBJECT_THRESHOLDS)
+
+    def test_default_matches_a_fresh_instance(self) -> None:
+        # the shared default must be value-equivalent to the previous
+        # per-call StationaryThresholds()
+        self.assertEqual(DEFAULT_OBJECT_THRESHOLDS, StationaryThresholds())
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/frigate/track/norfair_tracker.py b/frigate/track/norfair_tracker.py
index 3f11823572..7c695a7a7c 100644
--- a/frigate/track/norfair_tracker.py
+++ b/frigate/track/norfair_tracker.py
@@ -641,9 +641,11 @@ class NorfairTracker(ObjectTracker):
             self.deregister(self.track_id_map[e_id], e_id)
 
         # update list of object boxes that don't have a tracked object yet
-        tracked_object_boxes = [obj["box"] for obj in self.tracked_objects.values()]
+        tracked_object_boxes = {
+            tuple(obj["box"]) for obj in self.tracked_objects.values()
+        }
         self.untracked_object_boxes = [
-            o[2] for o in detections if o[2] not in tracked_object_boxes
+            o[2] for o in detections if tuple(o[2]) not in tracked_object_boxes
         ]
 
     def print_objects_as_table(self, tracked_objects: Sequence) -> None:
diff --git a/frigate/track/stationary_classifier.py b/frigate/track/stationary_classifier.py
index bea37f641b..1e22ec6f6d 100644
--- a/frigate/track/stationary_classifier.py
+++ b/frigate/track/stationary_classifier.py
@@ -63,6 +63,9 @@ NON_STATIONARY_OBJECT_THRESHOLDS = StationaryThresholds(
     max_stationary_history=4,
 )
 
+# Default thresholds for any other object label
+DEFAULT_OBJECT_THRESHOLDS = StationaryThresholds()
+
 
 def get_stationary_threshold(label: str) -> StationaryThresholds:
     """Get the stationary thresholds for a given object label."""
@@ -76,7 +79,7 @@ def get_stationary_threshold(label: str) -> StationaryThresholds:
     if label in NON_STATIONARY_OBJECT_THRESHOLDS.objects:
         return NON_STATIONARY_OBJECT_THRESHOLDS
 
-    return StationaryThresholds()
+    return DEFAULT_OBJECT_THRESHOLDS
 
 
 class StationaryMotionClassifier: