Hi Federico,
To give some some context, it looks like this happened to an airport uploaded from the World Hub.
All World Hub airports come with a polygon wrapped around them excluding TIN within their borders. Additionally, an automatic flattening is applied to World Hub airports, which really bothers me. (We cannot disable it in the World Hub.)
So far, I’ve seen two airports where we have had potential bugs from World Hub-submitted airports. One is this one, KMTH, which was submitted by Kai and then edited by a moderator. The TIN continues to be excluded outside the polygon, even though in all other World Hub airports, the falloff is 0.
Also KCDW, where only one user has reported an issue, where the entire airport is photogrammetry and there are no autogen buildings. That one was built by me, and it has an intact airport polygon with TIN exclusion.
My hope and guess is that these are issues that the World Hub team is working out, and the reason why they’re having the alpha.