I want to make a simple droplet application. I've set the document types to include com.adobe.pdf files, and I am now receiving callbacks to the app delegate's application(_:open:) callback when I drop PDFs on the app icon… But not the first time. It doesn't matter how long I wait, or whether the app is already open—the first drop never triggers the callback. All subequent drops work as expected, and I get URLs to all the files dropped. What might be wrong? How can I debug this?