Samsung made sure the Galaxy Note7 users are not able to insert the S-Pen backwards, and yet a new flaw seems to be plaguing some styluses.

Right now, it seems, the mechanical button on the S-Pen, which usually ejects the stylus from the silo, may stop clicking very soon. And no clicking simply means the S-Pen will not be ejected from the note. You could probably get it out with the aid of a pin, or alternatively, by hitting on the S-pen's hole, however, once you start having issues with it, you may be left with no choice than doing this quite often.

Currently, on YouTube, there are already a number of videos describing this issue and it is clearly the S-Pen fault

Check out these two YouTube video that will help explain the issue: http://www.techkibay.com/2016/08/samsungs-new-s-pen-keeps-getting-stuck.html