Just a guess on my part, having used chalk lines both for exterior work
and interior, is that you simply have too much chalk in the reel. I
have noticed that when I'm too lazy to reel it in before the next line
is snapped, there's still plenty of chalk available.
Try emptying the reel out completely and then pull out all of the line,
and snap it a couple of times, and finish up shaking the remainder out
of the reel and then reel it back in while running the line through an
old t-shirt to get as much of the chalk off of it.
Now - here's where I'm really guessing on how to proceed: Either pull
the line all the way out again and place just a small amount of chalk in
the reel before you reel it back in OR leave the line reeled in and
place just a small amount of chalk in there and see how it works after a
couple of line snaps.
My thought is that you're probably better off trying to recharge the
reel with chalk with the line fully extended and THEN reeling it in,
but, as I said, I'm just guessing on that.
What I'm not guessing at is that you simply have too much chalk coming out.