Shuttle drone improvements (#16931)

Content.Server/Shuttles/Systems/ShuttleSystem.cs

@@ -67,6 +67,13 @@ public sealed partial class ShuttleSystem : SharedShuttleSystem
         SubscribeLocalEvent<FixturesComponent, GridFixtureChangeEvent>(OnGridFixtureChange);
     }
 
+    public override void Shutdown()
+    {
+        base.Shutdown();
+        ShutdownGridFills();
+    }
+
+
     public override void Update(float frameTime)
     {
         base.Update(frameTime);