Reading tag text CoreNFC error 92

I've written a small test app to bring my understanding of CoreNFC up to snuff. The app just reads a tag and writes a simple string to it. The app has NFC entitlement, NFC privacy statement as required.

The app reports the tag has read/write capability.

When I read the tag message with NXP's 'TagWriter' app it states "This is a test" + current date. This is what I expect. When I read it with the app I wrote I get two chinese characters obscuring the first character i.e. capital 'T'. E.g. "<chinese>his is a test 2019-12-18 03:27:08". This is the method I use to extract the text:

func printNDEF(_ messages:[NFCNDEFMessage]) {
    DispatchQueue.main.async {
      for message in messages {
        for record in message.records {
          if let string = String(data: record.payload, encoding: .utf16) {
            print("MSG:\(string)")
          }
        }
      }
    }
  }

So please enlighten me what I do wrong here? Why is that first 'T' replaced by chinese whereas the NXP app does this correctly?

Then when I write to the tag the same string but with updated date/time. I get an error '92', LLDB reports; [CoreNFC] 00000002 83870f00 -[NFCNDEFReaderSession setAlertMessage:]:92 This is the method I use:

func doWriteTest(_ session: NFCNDEFReaderSession, tag:NFCNDEFTag) {
    print("Write Test")
    guard let record = NFCNDEFPayload.wellKnownTypeTextPayload(string: " This is a test \(Date())", locale: .current) else {
      return
    }
  
    let myMessage = NFCNDEFMessage.init(records: [record])
  
    tag.writeNDEF(myMessage) { (error) in
      if let error = error {
        session.alertMessage = "Write NDEF message fail: \(error)"
      }
      else {
        session.alertMessage = "Write NDEF message successful!"
      }
    }
  }

The method reports it was successful and the tag is indeed written to with the new date/time. No idea why I get error 92 and what it means. Note that I do have a session alert message, the NFC session is started with this:

func createNFCSession() {
    session = NFCNDEFReaderSession(delegate: self, queue: nil, invalidateAfterFirstRead: false)
    session?.alertMessage = "Hold phone near tag."
    session?.begin()
  }

Any help is much appreciated.