Hrm. Same results here. I get the same results with "And look around" at ~0:46, "Look around" at ~1:10, and "at the sky" at ~1:51 with both versions of the LRC. No immediate idea what the reason is.

One variable here is that you've got a lot of blank lines. Not that they should matter, but they're really making the scrolling do way too much... scrolling. You know? Why put in all those lines that it has to re-calculate scroll speed so much (even though it's not adding any text.) I think without all those extra lines, the scroll speed would be a little more stable, because it wouldn't be adding in extra space so much. My algorithm tends to throw space in to try to get the current "line" across the screen and also give you some space in between lines. Putting the blank line is putting this gap in twice, not necessary if you ask me. Still, my program shouldn't be having lines disappear just because of this, though in all instances I mention above, the "problem line" that's quickly disappearing is immediately preceeded and followed by a blank line (but so are other non-problematic lines in the song.)

<sarcasm>Why do I have a feeling this is going to be a really fun problem to debug.</sarcasm>