Why does this message appear?

When you execute a VLF-ONE application with Developer=YES on the URL, the creation and destruction of some major objects is tracked.

When an major object's uTerminate method is invoked, a delayed check is started to verify that the object's DestroyInstance event subsequently fires.

In other words, executing an object's uTerminate method implies that it should be subsequently destroyed.

If the DestroyInstance event is not fired, you may see a message like the preceding example.

Also see What should I do about this message?

Note: The existence of this VLF-ONE developer=YES object create/destroy tracking feature is absolutely no guarantee that your VLF-ONE application is not leaking resources in other ways that it cannot detect.