Fourth light stays on consistently and is blue.

[Trellis Blanton]

So Fred, my mouthpiece was cluttered with stuff inside the mouthpiece, so I had it cleaned. And after using a toothpick and then washing out the gunk out of the mouthpiece, the QuadStick started acting up.

The fourth light was blue and staying steady. It would not work. Then after checking the tubes and checking the mouthpiece, make sure it's dry, make sure there was nothing else in it. If it wasn't, it was still dry. It was still acting up.

I'm having to unplug and replug it in for it to work for a few minutes, and then it goes back to doing what it's doing. And so I unplugged all the tubing and for some reason, it was still showing fourth light blue.

So I don't think it's the mouthpiece anymore. I don't know what it could be, but that's all the information that I have. 

[Fred Davison]

I suspect water, or some other obstruction, has worked its way into the mp_right tubing or mouthpiece.

As the temperature changes the pressure of the air trapped behind the water changes.  Restarting the Quadstick allows it to recalibrate the zero-pressure reading, so it will work again for a while.

Try the other mouthpiece.