Changing to @Attribute(.ephemeral) worked for me too. Thanks @henningko !

Maybe it's because HKQuantitySample does not conform to Coddle, @rolandkajatin ? Not sure if it will work, but you could try using @Attribute(.transformable) by creating a struct than holds the info needed to recreate the HKQuantitySamples in your array...

Interacting with tvOS simulator: https://developer.apple.com/documentation/xcode/interacting-with-your-app-in-the-tvos-simulator