diff --git a/go/vehicle-gateway/internal/realtime/repository.go b/go/vehicle-gateway/internal/realtime/repository.go
index 6d629779..afd92a65 100644
--- a/go/vehicle-gateway/internal/realtime/repository.go
+++ b/go/vehicle-gateway/internal/realtime/repository.go
@@ -364,7 +364,7 @@ func asAnySlice(value any) ([]any, bool) {
 }
 
 func mergeSliceKey(item map[string]any) string {
-	for _, key := range []string{"name", "type", "id"} {
+	for _, key := range []string{"name", "type", "id", "serial_no"} {
 		if value, ok := item[key]; ok {
 			text := strings.TrimSpace(strconvAny(value))
 			if text != "" {
diff --git a/go/vehicle-gateway/internal/realtime/repository_test.go b/go/vehicle-gateway/internal/realtime/repository_test.go
index 7734f1f8..00df53c8 100644
--- a/go/vehicle-gateway/internal/realtime/repository_test.go
+++ b/go/vehicle-gateway/internal/realtime/repository_test.go
@@ -129,6 +129,73 @@ func TestRepositoryStoresFullParsedProtocolSnapshotAndMergesGB32960Units(t *test
 	}
 }
 
+func TestRepositoryMergesNestedGB32960MotorSlicesBySerialNo(t *testing.T) {
+	repo, closeFn := newTestRepository(t)
+	defer closeFn()
+	ctx := context.Background()
+
+	if err := repo.Update(ctx, envelope.FrameEnvelope{
+		Protocol:     envelope.ProtocolGB32960,
+		VIN:          "VIN001",
+		EventTimeMS:  1000,
+		ReceivedAtMS: 1100,
+		Parsed: map[string]any{
+			"data_units": []any{
+				map[string]any{
+					"type": "0x02",
+					"name": "drive_motor",
+					"value": map[string]any{
+						"motors": []any{
+							map[string]any{"serial_no": 1, "speed_rpm": 5000},
+							map[string]any{"serial_no": 2, "speed_rpm": 5100},
+						},
+					},
+				},
+			},
+		},
+	}); err != nil {
+		t.Fatalf("Update() error = %v", err)
+	}
+	if err := repo.Update(ctx, envelope.FrameEnvelope{
+		Protocol:     envelope.ProtocolGB32960,
+		VIN:          "VIN001",
+		EventTimeMS:  1100,
+		ReceivedAtMS: 1200,
+		Parsed: map[string]any{
+			"data_units": []any{
+				map[string]any{
+					"type": "0x02",
+					"name": "drive_motor",
+					"value": map[string]any{
+						"motors": []any{
+							map[string]any{"serial_no": 1, "speed_rpm": 5406},
+							map[string]any{"serial_no": 2, "speed_rpm": 5377},
+						},
+					},
+				},
+			},
+		},
+	}); err != nil {
+		t.Fatalf("Update() error = %v", err)
+	}
+
+	realtimeRaw, err := repo.GetRealtimeRaw(ctx, "VIN001", envelope.ProtocolGB32960)
+	if err != nil {
+		t.Fatalf("GetRealtimeRaw() error = %v", err)
+	}
+	units := realtimeRaw["data_units"].([]any)
+	driveMotor := units[0].(map[string]any)
+	value := driveMotor["value"].(map[string]any)
+	motors := value["motors"].([]any)
+	if len(motors) != 2 {
+		t.Fatalf("motors len = %d, want 2: %#v", len(motors), motors)
+	}
+	first := motors[0].(map[string]any)
+	if first["speed_rpm"] != float64(5406) {
+		t.Fatalf("first motor was not updated: %#v", motors)
+	}
+}
+
 func TestRepositoryOnlineStatus(t *testing.T) {
 	repo, closeFn := newTestRepository(t)
 	defer closeFn()