Erasing the Quadstick Configuration Flash

If the Quadstick is misconfigured and the flash drive is not available due to problem with the configuration files, first try to change to a different configuration file which may have flash access.  If that does not work, the flash can erased which will cause the Quadstick to revert to a simple configuration, similar to the Default Configuration, with controller modes in modes 1 through 4, and a mouse mode in mode 5. 
 

This should work with either the FPS or original models if the firmware is greater than 1142:

 
When the Quadstick powers up, it goes through sequence where the leds flash in a specific pattern.  While they are all flashing pink just after it is plugged in, push the lip button all the way in while simultaneously sipping on the center hole.  Hold that for several seconds after the boot up completes until the Quadstick resets again and all the lights start flashing pink.   If necessary, you can remove the tube for the center hole and have an assistant sip on it while holding the lip button all the way in.
 

For many original models:

 
While the leds are flashing pink, just after, but not before, power is applied, press directly in on the mouthpiece to activate the switch in the base of the joystick and hold it until a couple of seconds after the leds stop flashing.  This is probably too painful for you to do with your mouth.  An assistant can press in on the mouthpiece with both thumbs.  You should hear a click when the switch activates.
 
Afterwards, you can copy the Default Configuration and Default Preferences into the drive using QMP, then update the firmware to the latest version, then load in all your custom CSV files.
 

Keep a backup

 
You can copy the CSV files that configure the Quadstick to a folder on your computer to make it easy to recover from a misconiguration accident.