до

class ScanHandlerCallback implements android.os.Handler.Callback {
        @Override
        public boolean handleMessage(Message msg) {
            if (msg.what == WHAT_DISCONNECT) {
                stopScan();
                mainThreadHandler.sendEmptyMessageDelayed(WHAT_CONNECT, DELAY_CONNECT);
            }

            if (msg.what == WHAT_CONNECT && isScanning) {
                if (bluetoothAdapter != null && bluetoothAdapter.isEnabled()) {
                    scanner = bluetoothAdapter.getBluetoothLeScanner();
                }
                if (scanner != null) {
                    scanner.startScan(new ArrayList<>(), settings, bluetoothScanCallback);
                } else {
                    mainThreadHandler.post(() -> multiSenseObserverCallback.onError(ERROR_BLUETOOTH_DISABLED, null));
                }
                mainThreadHandler.removeCallbacksAndMessages(null);
                mainThreadHandler.sendEmptyMessageDelayed(WHAT_DISCONNECT, DELAY_DISCONNECT);
            }
            return true;
        }
    }

после

class ScanHandlerCallback implements android.os.Handler.Callback {
        @Override
        public boolean handleMessage(Message msg) {
            if (msg.what == WHAT_DISCONNECT) {
                stopScan();
                mainThreadHandler.sendEmptyMessageDelayed(WHAT_CONNECT, DELAY_CONNECT);
            }

            if (msg.what == WHAT_CONNECT && isScanning) {
                if (bluetoothAdapter != null && bluetoothAdapter.isEnabled()) {
                    scanner = bluetoothAdapter.getBluetoothLeScanner();
                }
                if (scanner != null && bluetoothAdapter != null && bluetoothAdapter.isEnabled()) {
                    scanner.startScan(new ArrayList<>(), settings, bluetoothScanCallback);
                } else {
                    mainThreadHandler.post(() -> multiSenseObserverCallback.onError(ERROR_BLUETOOTH_DISABLED, null));
                }
                mainThreadHandler.removeCallbacksAndMessages(null);
                mainThreadHandler.sendEmptyMessageDelayed(WHAT_DISCONNECT, DELAY_DISCONNECT);
            }
            return true;
        }
    }