After a while, everything wears out, 3d printer components included. I noticed, not too long ago, that my bowden tube kept slipping out of the pneumatic fitting attached to the extruder. Whenever the extruder would feed filament it would push the tube out too.

Upon investigation, I found that there are little “teeth” inside of the pneumatic fitting the keep the tube in place. Pushing down the little plastic ring disengages the teeth and allows the tube to slip out. Over time, the teeth had worn out and needed to be replaced. On most extruders, this is a simple fix. Just find the right size pneumatic fitting and replace it.