WCSession transferUserInfo only works in Foreground

I am using WCSession's tranferUserInfo to send data between the watch and the iOS app for info that needs to be handled when either product is in the background. This works 100% of the time on the simulator but never with actual devices.

By using breakpoints I have discovered that func session(session: WCSession, didReceiveUserInfo userInfo: [String : AnyObject]) is never called in the background but is immediately called when the app is brought to the foreground. Clearly session.transferUserInfo(data) is being called but not received in the background state. Again ruing the exact same code but on the simulator works perfectly.

I am ruing iOS 9.3.2 and Watch OS 2.2.1. Clearly this function was meant to handle communications in the background state and thus I believe the simulator is working as intended. I tried wrapping both the sender and receiver in a dispatch_async(dispatch_get_main_queue(), { block, but to no avail.

What am I missing about transferUerInfo and its seeming inability to work properly with background states?

FYI - breakpoint set at the begiing of didRecieveUserInfo is never hit until the app is brought into the foreground.

func transferInfo(data:[String: AnyObject])
    {
        dispatch_async(dispatch_get_main_queue(), {
            if #available(watchOSApplicationExtension 2.2, *)
            {
                if #available(iOS 9.3, *)
                {
                    if self.session.activationState == .Activated
                    {
                        self.session.transferUserInfo(data)
                    }
                    else
                    {
                        NSNotificationCenter.defaultCenter().postNotificationName("alertError", object: self, userInfo: ["error":"Failed to transfer"])
                    }
                }
                else
                {
                    self.session.transferUserInfo(data)
                }
            }
            else
            {
                self.session.transferUserInfo(data)
            }
        })
    }

func session(session: WCSession, didReceiveUserInfo userInfo: [String : AnyObject])
    {
        dispatch_async(dispatch_get_main_queue(), {
            for delegate in self.watchCommsProtocols
            {
                delegate.watchCommsDidUpdateInfo!(userInfo)
            }
        })
    }