I would have it looked at on your "warranty list". Most slides will close with the top contacting first and then the bottom draws up last and sometimes the bottom doesn't draw up as tight as the top. That makes sure that the top is sealed against rain, but, the bottom, less susceptible to rain, may not always pull up as tight. Probably, your slide was adjusted, but, not adjusted well enough for the difference to be barely noticeable. It is a simple adjustment and as long as the top is tight, not a major concern...just add it to the "list", but, definitely have it adjusted while you still have the warranty.