How to manual disconnect from BLE UART server

I added a setInterval to process the code ever 10 secs, the behaviour is now like this:

• sometimes it is processed "OK" with the overshoot and the "uncaught error BLE task .... progress"
  
• sometimes it result just in an "uncaught error ........ promise rejection", no data received
  
  

Maybe you know the source of the "uncaught error ........ promise rejection"?

Code and selection of output for reference below.

setInterval(function() {


var gatt;

print("Getting data from server");
  
NRF.connect("30:ae:a4:5d:b3:f2 public").then(function(g) {
  gatt = g;
  return gatt.getPrimaryService("6e400001-b5a3-f393-e0a9-e50e24dcca9e");
}).then(function(service) {
  return service.getCharacteristic("6e400003-b5a3-f393-e0a9-e50e24dcca9e");
}).then(function(characteristic) {
  characteristic.on('characteristicvaluechanged', function(event) {
    
    buf =E.toString(event.target.value.buffer);
    console.log("RX: "+buf);
    if(buf.includes("Quit")){
      print("Quit received, disconnecting now");
      gatt.disconnect();
    }
    
  });
  return characteristic.startNotifications();
}).then(function() {
  console.log("Done!");
});

}, 10000);

Output like this:

Getting data from server
Uncaught Error: Unhandled promise rejection: Disconnected
Getting data from server
Uncaught Error: Unhandled promise rejection: Disconnected
Getting data from server
Uncaught Error: Unhandled promise rejection: Disconnected
Getting data from server
RX: D07-06-2020 12.23
RX: SAAPL,311.01,+11.5%
RX: SASML,299.45,-4.5%
RX: Hottentottententente
RX: Quit
Quit received, disconnecting now
RX: D07-06-2020 12.23
Uncaught Error: BLE task 4 is already in progress
 at line 1 col 149
...ting now");gatt.disconnect();}
                              ^
in function called from system
RX: SAAPL,311.01,+11.5%
RX: SASML,299.45,-4.5%
RX: Hottentottententente
Uncaught Error: Unhandled promise rejection: Disconnected
Getting data from server
Uncaught Error: Unhandled promise rejection: Disconnected
Getting data from server
RX: D07-06-2020 12.23
RX: SAAPL,311.01,+11.5%
RX: SASML,299.45,-4.5%
RX: Hottentottententente
RX: Quit
Quit received, disconnecting now
RX: D07-06-2020 12.23
Uncaught Error: BLE task 4 is already in progress
 at line 1 col 149
...ting now");gatt.disconnect();}
                              ^
in function called from system
RX: SAAPL,311.01,+11.5%
RX: SASML,299.45,-4.5%
RX: Hottentottententente
Uncaught Error: Unhandled promise rejection: Disconnected
Getting data from server
Uncaught Error: Unhandled promise rejection: Disconnected
Getting data from server
Uncaught Error: Unhandled promise rejection: Disconnected
Getting data from server
RX: D07-06-2020 12.23
RX: SAAPL,311.01,+11.5%
RX: SASML,299.45,-4.5%
RX: Hottentottententente
RX: Quit
Quit received, disconnecting now