Tween crash (3.4 KB)

This is totally random but I found two innocuous-looking curves that crash Tween. (I used the Pufferfish tween, with a different match method, as a workaround.)

These curves do not work with anything, not loft or ruled surface, or tween, which gave me an idea to look at the end points and found that you have duplicated control points on the ends (this is the usual reason loft fails and gives the “don’t know why” error" - the other being when the start and end curve of a closed loft are a duplicate curve.)

Delete one of them and everything works: