I had a KT-1 (same head, different lamp assembly) and used in on my M2. I did not hace thisproblem.
I'd suggest either pulling the clip (I have found them unusable on my 3x123 cell lights) or pull it and reset it.
Remove the o-ring, then pull off the clip (watch for the little black piece of plastic that lies underneath the clip). You can then reinstall it, if you wish, pushing it in far enough to clear the KT-1 collar.