I'm into FSE which has a very obsolete airport list (based on FS9 I think). Thus, many airports in it are now defunct and do not exist in MSFS, so I have resurrected a number of them with the MSFS SDK. And they work for a while, showing up on the World Map and functioning in-game. But after a while, many of them cease to show up on the World Map, even with no changes to their files. They just go away. Sometimes, if I start the whole project over from scratch, they will reappear briefly, then go away again. Sometimes nothing I do brings them back. And it appears to be that the SDK and/or MSFS itself is checking the ICAO and killing the airport if the code's not on the list. However, this check doesn't always happen.
Here's an example: EKRR, Rø, Denmark, which is now a golf course. I built this (very simple) airport in 1 go from start to finish, built the package with no errors, and it worked just fine. For a day or so. Then it stopped. I opened the project again just now to maybe try to fix it, and noticed this error:
After tweaking this and that, saving the scenery, and rebuilding the package, it STILL failed to appear on the World Map, like it's been blackballed.
NOTE: This has pretty serious implications for fictitious airports as well.
How do you get around this? Thanks in advance.
Here's an example: EKRR, Rø, Denmark, which is now a golf course. I built this (very simple) airport in 1 go from start to finish, built the package with no errors, and it worked just fine. For a day or so. Then it stopped. I opened the project again just now to maybe try to fix it, and noticed this error:

After tweaking this and that, saving the scenery, and rebuilding the package, it STILL failed to appear on the World Map, like it's been blackballed.
NOTE: This has pretty serious implications for fictitious airports as well.
How do you get around this? Thanks in advance.