ios - Why are my FaceTime Group Activities getting out of sync from each other?

Question

I am testing out the new FaceTime API's for Shared activities. Even though I followed along with the developer sessions, my data will occasionally get out of sync. I belive it may have something to do with the runtime error I am getting below.

"Publishing changes from background threads is not allowed; make sure to publish values from the main thread (via operators like receive(on:)) on model updates." Line

The developer sessions show the sending and receiving call's to the API as asynchronous.

@Published var groupSession: GroupSession<DrawTogether>?
var messenger: GroupSessionMessenger?

func configureGroupSession(_ groupSession: GroupSession<DrawTogether>){
    reset()
    
    let messenger = GroupSessionMessenger(session: groupSession)
    self.messenger = messenger
    self.groupSession = groupSession
    

    groupSession.$activeParticipants
        .sink { activeParticipants in
            let newParticipants =
                activeParticipants.subtracting(groupSession.activeParticipants)
            
            async {
                do {
                    try await messenger.send(CanvasMessage(elements: self.elements), to: .only(newParticipants))
                } catch {
                    print("Unable to update new participants")
                }
            }
            
        }
        .store(in: &subscriptions)

    let emojiTask = detach { [weak self] in
        for await (message, _) in messenger.messages(of:
            UpsertEmojiMessage.self){
            await self?.handle(message)
        }
    }
    tasks.insert(emojiTask)
    
    let task = detach { [weak self] in
        for await (message, _) in messenger.messages(of: CanvasMessage.self) {
            await self?.handle(message)
        }
    }
    tasks.insert(task)
    
    groupSession.join()
}

func handle(_ message: UpsertEmojiMessage) {
    let element = Element(emoji: message.emoji, postion: message.position)
    elements.append(element)
}

func handle(_ message: CanvasMessage) {
    //guard message.elements.count > self.elements.count else { return }
    self.elements = message.elements // Warning occurs on this line
}