I noticed that if you rename a Form that you’ve previously Set as startup form, you get the following error when you run your app:
The error message is somewhat misleading, but if you’re lucky you’ll realise that you need to manually do Set as startup form again on your newly renamed Form.
The error could be avoided entirely if the Rename… function itself checked for Set as startup form and reapplied that status to the renamed Form automatically, rather than creating an ‘orphan’.