I've got the rest of test chamber 08 glitchless pretty ok, but what goes wrong more often than not is my momentum while jumping through a portal. First attempt here is a crouch jump where it just halts me in midair, you can see my velocity jump from 260 down to 115 as I go through. Second is me trying to inch forward and jump without crouching, going from 75 to 280 in one frame and the third is a regular crouch jump and well, I assume that's a known glitch but I have no idea how I did it. I was holding W through the portal the first and last times, if that helps.

Am I hitting the sides of the portal without realizing? The ceiling? Am I jumping too early or late? This is driving me nuts, any help would be appreciated.