I'm also running into this issue, my app crashes almost every time I unblock my phone in the background on iOS 18.4... no changes to the codebase between iOS 18.3.2 and the latest iOS 18.4 beta I'm also utilizing hourly steps for HealthKit background delivery. Would love to see a fix, filed a bug ticket as FB17063126 Thanks so much for your help in this thread @DTS Engineer. __ Andreas Ink

I also am having this issue however, it appears to go away once I removed roomSession.stop() that was being called before the session started

I did find a workaround for this, simply wrap your Data object in a Codable struct, like this... struct DrawingData: Codable { var data: Data init(data: Data) { self.data = data } } When you initialize the Model class, make sure to call an init with drawingData (or whatever variable type, as long as it's a codable struct) that is of type DrawingData (or whatever you rename this to). Prior to wrapping the Data object, I had the same crash you all are reporting. I also filed feedback :)

Similar issue, solved by unpairing my old watch and connecting Xcode and toggling developer mode on the watch directly