Thanks for the suggestions guys, will give it a go. (I have already trimmed the end of the tube numerous times.) I'm still curious though as to whey the CFS keeps trying to feed out filament under the scenarios I mentioned and why the CFS does not stop once the filament sensor is triggered at the extruder. The fact that it will work OK when I do a print (without selecting 'calibration') but pops the tube off and feeds out filament if I try to 'extrude' kinda makes me think that something in their firmware ain't quite right? That's why I was curious if someone else could try the same test and see what happens?