Update: Based on this https://www.swiftbysundell.com/articles/the-main-actor-attribute/#custom-ui-related-classes, I don’t believe with the above solution that the compiler any longer guarantees that cancelled() is called on the main actor (though in practice it will be, because Button will fire its action on the main actor).

I’m afraid not, no. The only reason I’m able to make any sense whatsoever of these errors is that I currently have access to a codebase with thousands of users and good device analytics, which I can mess around with to produce charts of errors against device age and OS etc. That’s how I figured out the differences that newer devices are showing.

That’s right. My 'store' uses reflection (Mirror.descendant()) to find a given model instance inside its storage. The Store.find<M:Model>(type:M) -> M? performs the find.