Why it's working on the video? ;)
Because there is previously a fillet at the start of the internal volume! ;)
There is a minimal thickness! It's not a real Sharp angle!
Flippy, try using G3 with ~1 bulge for your case. It seems to work better. I gave it a shot at the tut from the start, and it worked for me. Sometimes when there are corner points next to each other, things get tricky, but spending time with MoI will give you a feel for what could work better and which point is problematic. Good luck!
