diff --git a/ssbo_component/ssbo_editor.py b/ssbo_component/ssbo_editor.py
index e18f63f7..082c8489 100644
--- a/ssbo_component/ssbo_editor.py
+++ b/ssbo_component/ssbo_editor.py
@@ -735,7 +735,8 @@ class SSBOEditor:
                 return False
 
         try:
-            source_node.set_mat(self.source_model_root, current_net_mat)
+            reference_node = self._get_transform_snapshot_reference_node(source_node)
+            source_node.set_mat(reference_node, current_net_mat)
             source_node.setTag("scene_transform_dirty", "true")
             try:
                 self._cache_top_level_source_child_base_mat(source_node, source_node.get_mat())
@@ -747,7 +748,7 @@ class SSBOEditor:
             return True
         except Exception:
             try:
-                source_node.setMat(self.source_model_root, current_net_mat)
+                source_node.setMat(reference_node, current_net_mat)
                 source_node.setTag("scene_transform_dirty", "true")
                 try:
                     self._cache_top_level_source_child_base_mat(source_node, source_node.get_mat())
@@ -807,7 +808,8 @@ class SSBOEditor:
                 # Use robust Panda3D set_mat(ref, mat) to handle all coordinate conversions.
                 # This ensures the source node's net transform relative to the source root
                 # exactly matches the runtime node's net transform relative to self.model.
-                source_node.set_mat(self.source_model_root, current_net_mat)
+                reference_node = self._get_transform_snapshot_reference_node(source_node)
+                source_node.set_mat(reference_node, current_net_mat)
                 source_node.setTag("scene_transform_dirty", "true")
                 
                 # Update top-level child baseline cache for structural sync
@@ -1093,7 +1095,8 @@ class SSBOEditor:
 
         try:
             # Corrected: use Panda3D native world-to-local projection relative to source root
-            source_node.set_mat(self.source_model_root, current_net_mat)
+            reference_node = self._get_transform_snapshot_reference_node(source_node)
+            source_node.set_mat(reference_node, current_net_mat)
             source_node.setTag("scene_transform_dirty", "true")
             try:
                 self._cache_top_level_source_child_base_mat(source_node, source_node.get_mat())
@@ -1132,6 +1135,48 @@ class SSBOEditor:
                 return None
         return node
 
+    def _is_node_in_subtree(self, node, subtree_root):
+        if not self._node_is_valid(node) or not self._node_is_valid(subtree_root):
+            return False
+        current = node
+        while self._node_is_valid(current):
+            if current == subtree_root:
+                return True
+            try:
+                current = current.get_parent()
+            except Exception:
+                try:
+                    current = current.getParent()
+                except Exception:
+                    return False
+        return False
+
+    def _get_transform_snapshot_reference_node(self, source_node):
+        """
+        Pick the correct reference node when snapshotting runtime transforms.
+
+        In the single-top-level-model path, the runtime moves that only top-level
+        child transform onto self.model. Descendant runtime matrices are then
+        relative to the sole source child, not to source_model_root. Saving those
+        descendants against source_model_root bakes the inverse root transform into
+        children, so reopening restores children but loses the whole-model pose.
+        """
+        source_root = self.source_model_root
+        if not self._node_is_valid(source_node) or not self._node_is_valid(source_root):
+            return source_root
+
+        source_children = self._get_source_root_children()
+        if len(source_children) != 1 or not self._node_is_valid(source_children[0]):
+            return source_root
+
+        sole_source_child = source_children[0]
+        if source_node == sole_source_child:
+            return source_root
+
+        if self._is_node_in_subtree(source_node, sole_source_child):
+            return sole_source_child
+        return source_root
+
     def _resolve_tree_key_for_source_node(self, node):
         """Resolve a source-tree NodePath back to the controller tree key."""
         source_root = self._ensure_source_model_root()