The above instructions for updating the firmware have worked for me. I have been upgraded to 4.13.11-0 (from 4.12.6-0)
Note: for some reason I assumed I should replace the batteries after having taken them out for a few seconds, then proceeding with the keypress+connect step. This was preventing my device from entering DFU/bootstrapper mode. Things went much better when I remembered how to read :)
"To safely enter bootloader mode. Take out the batteries. press the middle cursor button, and the back button. while plugging it into the computer. See attached.
If successful, pressing any button will blink the LED 3 times. If so, start the app, it should force an update."