The actual base of the coil? ...Yes, can see that it comes right out - mine just flew across the room! Soon found it though and I'll try it when I change the coil...see what happens. Surely though, if I can just pull it out with my fingers, it'll go back in again as soon as it meets the slightest resistance?
The ego threaded atomisers work best when you screw them in till you feel the slightest resistance (in my experience). If you over tighten them the wire legs of the coil can get screwed up and it can cause shorts or inconsistant resistance (ohms) readouts. When you over tighten them onto your battery the rubber insulator gets squashed and if you leave it that way for any length of time it never recovers its' original size, sometimes leading to the problems you're having



...I had a bath last month, so it can't be that