I have the exact same problem sometimes, It happens with the sensor, I am not exactly sure how to fix it, It happens mostly as a sign it's dirty, but if I let it happen persistently Its tougher to fix, and sometimes will not fix its self by cleaning first try. I just clean my latch really really good, that helps, also if I am out and about and cant clean, I'll hold the mouthpiece indented just a tiny bit (an 16th- to an 8th inch indented), this will actually solve your problem every time. (Well for me any way) Sometimes pressing the mouthpiece all the way down past the second click helps too, if the magnet isnt engaging this will fix that, I doubt this happens much, I only see the magnet not engage on my bong adapter, but it does happen occasionally and requires me to put a normal mouthpiece in first. Removing the adapter and reinserting the normal mouthpiece almost always works.