Not only does the compressor get hot from the friction of the piston but the Ideal Gas Law states that increasing the pressure of a gas increases its temperature. The compressed air from the compressor is actually hotter than ambient. If you run it for a long time it would be conceivable that the tube gets heated by the compressed air to a point where it can no longer withstand its designed working pressure and you see the bubbling that you showed.
A short metal pipe attached to the compressor would help to dissipate this heat.
Or let your system coll a bit in between runs.
EDIT: looks like John beat me to it
