diff --git a/src/textual/app.py b/src/textual/app.py
index 07b5e4f1a3..c22875427a 100644
--- a/src/textual/app.py
+++ b/src/textual/app.py
@@ -2752,23 +2752,24 @@ def is_mounted(self, widget: Widget) -> bool:
     async def _close_all(self) -> None:
         """Close all message pumps."""
 
-        # Close all screens on all stacks:
-        for stack in self._screen_stacks.values():
-            for stack_screen in reversed(stack):
-                if stack_screen._running:
-                    await self._prune_node(stack_screen)
-            stack.clear()
-
-        # Close pre-defined screens.
-        for screen in self.SCREENS.values():
-            if isinstance(screen, Screen) and screen._running:
-                await self._prune_node(screen)
-
-        # Close any remaining nodes
-        # Should be empty by now
-        remaining_nodes = list(self._registry)
-        for child in remaining_nodes:
-            await child._close_messages()
+        async with self._dom_lock:
+            # Close all screens on all stacks:
+            for stack in self._screen_stacks.values():
+                for stack_screen in reversed(stack):
+                    if stack_screen._running:
+                        await self._prune_node(stack_screen)
+                stack.clear()
+
+            # Close pre-defined screens.
+            for screen in self.SCREENS.values():
+                if isinstance(screen, Screen) and screen._running:
+                    await self._prune_node(screen)
+
+            # Close any remaining nodes
+            # Should be empty by now
+            remaining_nodes = list(self._registry)
+            for child in remaining_nodes:
+                await child._close_messages()
 
     async def _shutdown(self) -> None:
         self._begin_batch()  # Prevents any layout / repaint while shutting down
@@ -3342,7 +3343,10 @@ async def prune_widgets_task(
                 await self._prune_nodes(widgets)
             finally:
                 finished_event.set()
-                self._update_mouse_over(self.screen)
+                try:
+                    self._update_mouse_over(self.screen)
+                except ScreenStackError:
+                    pass
                 if parent is not None:
                     parent.refresh(layout=True)