What you're looking at there maybe the sky boxes. Hide the top or side planes of the the big one and look inside or put the model in to wireframe mode and see what you find inside them.

Hmmm. then again I downloaded your blend file and all there are are angled planes inside.

Is the map supposed to look like those 3 stacked cubes without anything inside them?

Before exporting the SMDs, do a Ctrl+A and apply all transforms, then export the SMDs.

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2504104433

Hello thanks, sorry for the late response, I didn't expect to get a reply. I will try your tip soon.

And yes they are supposed to look like the first 2 screenshots.