Close event fires twice

I set the default page of my web app to a startup page (PgStartup). That page has a WebTimer that calls a method on Session.DoStartup, and that method will show the right page based on conditions. Then the WebTimer calls self.Close.

Action()
  Session.DoStartup()
  self.Close

This works fine except the PgStartup.Close event fires twice. If I remove the call to self.Close, it doesn’t fire at all. Bug or have I missed something?

I filed Feedback because this seems like a bug.

<https://xojo.com/issue/41455>