I had a mishap recently which required me to remove my bowden tube from my printer in order to clear out a clog. Upon reassembly, the tube kept popping out of the connector whenever I would try to print something.

As it turns out, there are tiny little “teeth” inside of the pneumatic connector that keep the bowden tube in place. When I removed it the first time, I smashed some of the teeth and prevented it from grabbing the tube properly.

In order to fix the situation, I replaced the tube itself (been meaning to do that for quite a while) and the pneumatic coupling.