Getting a BLE error trying to get Puck to talk to Bangle

Hey all, I'm a little lost here. My Bangle is running a watchface that is listening on a specific UUID for short strings to act as notifications (not BLE notifications, just messages). The Bangle code works fine, and I can access it from both a Web Bluetooth page and a DroidScript app. However, I can't get my puck to send the message properly. Here is the Bangle (peripheral) code snippet:

var BLEMessage = "";
NRF.setServices({
  "feb10001-f00d-ea75-7192-abbadabadebb": {
    "feb10002-f00d-ea75-7192-abbadabadebb": {
      value : [0],
      maxLen : 20,
      writable : true,
      onWrite : function(evt) {
        let str = stringFromArray(evt.data);
        if(str === "__EOM__") {
          if(BLEMessage) {
            showMsg('Message',BLEMessage);
          } else {
            reload();
            scheduleAlarms();
            showMsg('', 'Reloading...');
          }
          BLEMessage = '';
        } else {
          BLEMessage += str;
        }
      }
    }
  }
}, { });

The showMsg() function is defined and works fine (just draws a dialog box and writes the string to screen).

Here is the Puck code (mostly thanks to Gordon's BLE example):

const primaryServiceUuid = 'feb10001-f00d-ea75-7192-abbadabadebb';
const sendCharUuid = 'feb10002-f00d-ea75-7192-abbadabadebb';

let device, sendCharacteristic;


const split20 = (msg) => {
  let chunks = [];
  while(msg.length > 20) {
    chunks.push(msg.substr(0, 20));
    msg = msg.substr(20);
  }
  if(msg.length) chunks.push(msg);
  return chunks;
};

var msgToSend = "FOO!";
var logMsg = '';

function logD() {
  require("Storage").write('logMsg.txt', logMsg);
}

function sendMsg() {
  var gatt;
   NRF.requestDevice({  filters: [{ namePrefix: 'Bangle' }]  })
  .then(function(device) {
    logMsg += "Found\n";
    digitalPulse(LED2,1,10);
    return device.gatt.connect();
  }).then(function(g) {
    logMsg += "Connected\n";
    digitalPulse(LED3,1,10);
    gatt = g;
    return g.getPrimaryService(primaryServiceUuid);
  }).then(function(service) {
    logMsg += "got PS\n";
    return service.getCharacteristic(sendCharUuid);
  }).then(function(characteristic) {
    logMsg += "Got char\n";
    sendCharacteristic = characteristic;
    return sendCharacteristic.writeValue(toArrBuf(myMessage));
  }).then(function() {
    logMsg += "Sending: " + JSON.stringify(toArrBuf(myMessage));
    return sendCharacteristic.writeValue( toArrBuf('__EOM__'));
  }).then(function() {
    digitalPulse(LED2,1,[10,200,10,200,10]);
    gatt.disconnect();
    logMsg += "Done!\n";
    logD();
    busy=false;
  }).catch(function(e) {
    digitalPulse(LED1,1,10);
    logMsg += e.toString()+"\n";
    busy=false;
    logD();
  });
}


setWatch(sendMsg, BTN, {edge:"rising", debounce:50, repeat:true});

Which works fine in an HTML page using "let NRF = navigator.bluetooth;"
I'm writing my log to a file since console is disabled when I run this, and the file reads:

Found
Connected
BLE error 0x11 (BUSY)

As i said, I know the Bangle code works, been using it for weeks. The Puck code runs in a browser just fine. Which device is "BUSY"?? Any help appreciated!