This is surely operator error and I try to be careful and mindful, but nevertheless, the elbow connector pops off as I am trying to connect or disconnect the vac hose. This happens maybe 10% of the time, just enough to be super-annoying. anyone else run into this? Any way to make it more secure or adjust whatever bad technique I have? I do try to carefully line up the notches, insert hose, and twist. Like I said, it _usually_ works just fine, so I am almost doing it right.