AMP lightcrimp plus problem

Just bought the AMP lightcrimp plus termination kit, and I am having a problem 
with the crimper.  I insert the fiber all the way in to the plunger, but, as I 
crimp the cable the act of crimping nudges the fiber buffer back out about 
2/16", which renders the connector useless cause it isnt mating with the 
internal fiber.  Im gonna call AMP on Monday, cause I am sure I am missing 
something.  Anyone, have a little clue on what I may be doing to cause this?
I was terminating a ST connector. 

Thanks

Jim