My fix for the missing line issue was to place timing points at negative times, and displace the lines to their proper locations.

I made a Desmos graph for the line trajectories: www.desmos.com/calculator/h...

Empty frames of the line art animation are made by successive teleports and 0x SVs. In my first attempt at line art, you can see that the bottom two lines show up late. This is due to the timing points being placed too close to each other time-wise, which causes the game to not render them.

He shared his file in the mapping channel. I had actually been independently experimenting with the effect a few days prior, and so after an hour got the effect working with even note spacing.