I just found out how to fix it.
HOW TO FIXThis error is caused by Starforge. If you exit using the top right X, Xtra will read the file as "write protected". Heres how to fix.
1. Open up starforge.
2. Open your map. Theres a possibility that errors will occur (it happened to me). You should be able to press "yes" or "ok" to get past it, and your map will load.
3. File > Save.
4. File > Exit (NOT THE TOP RIGHT X).
There. Your map is how it was. Your wavs might need reimporting though

Heimdal needs to slow down a bit with the features I think
I still can't manage to cause the error on purpose. Did you ever try to cause this error by doing this or is this just what you think you did. Also when you close with the X it gives you a save message did you click yes no? Tell me if you can cause the error in a new map. Nothing is a valid bug you can report unless you can purposely cause the bug again.
If you want to read more on this subject there is currently another thread about it at blizz forums