The "mistake" of a boost that happens at the end of bluecheetah's IL of 1-4 had me stumped for a while. https://www.speedrun.com/qbeh1/run/pydj6njy

Through testing, I found out and put together some things. First we know that an uncontrolled teleport will move you at very high velocity towards the coordinates 1000, 1000, 1000 (technically not a teleport). And we know that we can control this teleport by starting it, but aiming and placing the block down in our new desired location. But there is a very brief window, after you have started the teleport, that you start getting dragged away at high speed, you can still place your cube in the desired location for your controlled teleport. This will result in varying degrees of accelerated momentum toward 1000, 1000, 1000, while still teleporting you to where you want to go, and while in that semi-confined environment, you end up bouncing around, and sometimes land on the ledge higher.

Thus, now we kind of know what's going on, but making that happen in an IL or run with consistency, that's gonna be the tough part.