I don‘t think it‘s your code that is the issue. I‘m facing the exact same problem here, and I think that is rather a thing that Apple has to fix. There is a reason why below the toggle it warns you that you may experience lag. On my playground, I have just put in a reminder that tells you to Disable Results before running.

All of them are accepted! You can submit both an Xcode Playground or a Swift Playground for Mac or iPad. Just remember that you are not allowed to submit an app, you can only submit a Playground as of this year.

They also mention that your playground will be judged offline, meaning that WiFi will not be enabled. As a reminder, here‘s what they say: „Submissions will be judged offline. Your Swift playground should not rely on a network connection and any resources used in your Swift playground should be included locally in your ZIP file.“ Sorry to disappoint you.