Navmesh data doesn't save on project exit, what do I do?

Hey, I have a problem where the navmesh, as seen in the image below…


It doesn’t get saved on project exit…
Meaning, when I exit the project, and enter it again, the navmesh needs to rebuild again.

However I did notice something strange, which is that it appears built on a certain part of the navmesh area, so I find that strange.
As seen below:

To re-iterate, my goal right now is that I want the navmesh data to be saved and loaded on project exit/start
How to do that?

Oh also I have this in my outliner:

Hey I just want to say… the most probable cause for this is the navmesh size.
I know… crazy huh?

The size shouldn’t be bigger than 100 XYZ from what I’ve seen.
Only then… it can save the navmesh data.