diff --git a/CHANGELOG.md b/CHANGELOG.md
index a668b8f6..6774df82 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,9 +1,9 @@
 # Changes in Fbx Exporter
 
-## [Unreleased]
+## [5.1.6] - 2026-03-30
 ### Changed
 - Replaced obsolete `EntityId.GetRawData()` with `EntityId.ToULong(EntityId)` (warning CS0618).
-- Replaced obsolete `SearchService.GetItems` with `SearchService.Request`(warning CS0618).
+- Replaced obsolete `SearchService.GetItems` with `SearchService.Request` (warning CS0618).
 
 ## [5.1.5] - 2025-09-24
 ### Changed
diff --git a/com.unity.formats.fbx/Tests/FbxTests/ConvertToModelTest.cs b/com.unity.formats.fbx/Tests/FbxTests/ConvertToModelTest.cs
index 0580d8f1..2806b993 100644
--- a/com.unity.formats.fbx/Tests/FbxTests/ConvertToModelTest.cs
+++ b/com.unity.formats.fbx/Tests/FbxTests/ConvertToModelTest.cs
@@ -517,39 +517,39 @@ public void TestStaticHelpers()
 
                 Assert.That(bReferenceComponent.m_transform.name, Is.EqualTo(a.transform.name));
             }
+        }
 
-            // Test GetSceneReferencesToObject()
-            {
-                var a = GameObject.CreatePrimitive(PrimitiveType.Cube);
-                var b = new GameObject();
-                var c = new GameObject();
-
-                var reference = b.AddComponent<ReferenceComponent>();
-                var constraint = c.AddComponent<UnityEngine.Animations.PositionConstraint>();
-
-                reference.m_collider = a.GetComponent<BoxCollider>();
-
-                var constraintSource = new UnityEngine.Animations.ConstraintSource();
-                constraintSource.sourceTransform = a.transform;
-                constraintSource.weight = 0.5f;
-                constraint.AddSource(constraintSource);
-
-#if !UNITY_2021_2_OR_NEWER
-                var sceneRefs = ConvertToNestedPrefab.GetSceneReferencesToObject(a);
-                Assert.That(sceneRefs.Count, Is.EqualTo(2));
-                Assert.That(sceneRefs.Contains(a)); // GameObjects also reference themself
-                Assert.That(sceneRefs.Contains(b));
-
-                sceneRefs = ConvertToNestedPrefab.GetSceneReferencesToObject(a.GetComponent<BoxCollider>());
-                Assert.That(sceneRefs.Count, Is.EqualTo(1));
-                Assert.That(sceneRefs.Contains(b));
-
-                sceneRefs = ConvertToNestedPrefab.GetSceneReferencesToObject(a.transform);
-                Assert.That(sceneRefs.Count, Is.EqualTo(2));
-                Assert.That(sceneRefs.Contains(b));
-                Assert.That(sceneRefs.Contains(c));
-#endif // !UNITY_2021_2_OR_NEWER
-            }
+        // Same rationale as TestReferencesInScene: hierarchy search may not see script-created refs until a frame is skipped.
+        [UnityTest]
+        public IEnumerator TestSceneObjectReferrersSearch()
+        {
+            var a = GameObject.CreatePrimitive(PrimitiveType.Cube);
+            var b = new GameObject();
+            var c = new GameObject();
+
+            var reference = b.AddComponent<ReferenceComponent>();
+            var constraint = c.AddComponent<UnityEngine.Animations.PositionConstraint>();
+
+            reference.m_collider = a.GetComponent<BoxCollider>();
+
+            var constraintSource = new UnityEngine.Animations.ConstraintSource();
+            constraintSource.sourceTransform = a.transform;
+            constraintSource.weight = 0.5f;
+            constraint.AddSource(constraintSource);
+
+            yield return null;
+
+            // Exact result counts vary by Unity version (search may list extra referrers, e.g. constraints vs colliders).
+            var sceneRefs = GetSceneRefsForTest(a);
+            Assert.That(sceneRefs, Has.Member(a)); // GameObjects also reference themself
+            Assert.That(sceneRefs, Has.Member(b));
+
+            sceneRefs = GetSceneRefsForTest(a.GetComponent<BoxCollider>());
+            Assert.That(sceneRefs, Has.Member(b));
+
+            // b only references the BoxCollider on a, not a.transform; Search may omit b here. c references a.transform.
+            sceneRefs = GetSceneRefsForTest(a.transform);
+            Assert.That(sceneRefs, Has.Member(c));
         }
 
         [Test]
@@ -792,5 +792,15 @@ public void TestUndoNameReset()
             // Make sure name is same as original
             Assert.AreEqual("cube 1", cube.name);
         }
+
+        // GetSceneReferences (2021.2+) vs hierarchy search on older Unity; same assertions for both.
+        static List<Object> GetSceneRefsForTest(Object obj)
+        {
+#if UNITY_2021_2_OR_NEWER
+            return ConvertToNestedPrefab.GetSceneReferences(obj);
+#else
+            return new List<Object>(ConvertToNestedPrefab.GetSceneReferencesToObject(obj));
+#endif
+        }
     }
 }
diff --git a/com.unity.formats.fbx/Tests/FbxTests/ModelExporterTest.cs b/com.unity.formats.fbx/Tests/FbxTests/ModelExporterTest.cs
index a14d8c3d..956a5874 100644
--- a/com.unity.formats.fbx/Tests/FbxTests/ModelExporterTest.cs
+++ b/com.unity.formats.fbx/Tests/FbxTests/ModelExporterTest.cs
@@ -88,17 +88,21 @@ public void TestBasics()
                 var character = new GameObject();
                 var smr = character.AddComponent<SkinnedMeshRenderer>();
                 smr.sharedMesh = cube.GetComponent<MeshFilter>().sharedMesh;
-#if UNITY_2023_1_OR_NEWER
+#if UNITY_6000_4_OR_NEWER
+                var meshCount = Object.FindObjectsByType<Mesh>().Length;
+#elif UNITY_2023_1_OR_NEWER
                 var meshCount = Object.FindObjectsByType<Mesh>(FindObjectsSortMode.None).Length;
-#else // UNITY_2023_1_OR_NEWER
+#else
                 var meshCount = Object.FindObjectsOfType<Mesh>().Length;
-#endif // UNITY_2023_1_OR_NEWER
+#endif
                 ModelExporter.ExportObject(GetRandomFbxFilePath(), character);
-#if UNITY_2023_1_OR_NEWER
+#if UNITY_6000_4_OR_NEWER
+                Assert.AreEqual(meshCount, Object.FindObjectsByType<Mesh>().Length);
+#elif UNITY_2023_1_OR_NEWER
                 Assert.AreEqual(meshCount, Object.FindObjectsByType<Mesh>(FindObjectsSortMode.None).Length);
-#else // UNITY_2023_1_OR_NEWER
+#else
                 Assert.AreEqual(meshCount, Object.FindObjectsOfType<Mesh>().Length);
-#endif // UNITY_2023_1_OR_NEWER
+#endif
             }
 
             // Test euler to quaternion conversion
diff --git a/com.unity.formats.fbx/package.json b/com.unity.formats.fbx/package.json
index b68ef4f2..ba2c2bb0 100644
--- a/com.unity.formats.fbx/package.json
+++ b/com.unity.formats.fbx/package.json
@@ -1,10 +1,10 @@
 {
   "name": "com.unity.formats.fbx",
   "displayName": "FBX Exporter",
-  "version": "5.1.5",
+  "version": "5.1.6",
   "dependencies": {
     "com.unity.timeline": "1.7.1",
-    "com.autodesk.fbx": "5.1.1"
+    "com.autodesk.fbx": "5.1.3"
   },
   "unity": "2020.3",
   "description": "The FBX Exporter package enables round-trip workflows between Unity and 3D modeling software. Send geometry, Lights, Cameras, and animation from Unity to Autodesk® Maya®, Autodesk® Maya LT™, or Autodesk® 3ds Max®, and back to Unity again, with minimal effort.",