A common problem with Montblanc pens (and basically all vintage pens) is that fillings change over the course of years. One of these issues occur with the Montblanc S-Line pens.
At some point Montblanc decided to change the depth of the hole in the back of the filling and make it deeper. (Blue being the modern filling)
The pusher has a certain length that is exactly right to push out the original filling.
However, using a modern filling, the tip doesn’t come out all the way.
The fix is relatively simple, just take a standard issue leaf of toilet paper and take out a small square as seen below.
Roll it into a tiny ball
Press it into the hole
And voila, the tip goes out far enough
If it didn’t work the first time, just take out the tiny ball and increase or decrease the size to improve results