@Andrey: from MarkShot9(Steam) but via screen shots

[MarkShot]

Create a new mission.





Save it with filename "andre.mispack" (sorry misspelled your name)







Please note the file's timestamp:  07:27pm and system time 07:28pm.

Now, let's modify and add two more platoons.





We want to replace the original mission.







It looks good from the next screen.



But notice the file time stamp and the later system time.



Finally, we open the mission and as guessed, it was never updated.  I believe this because MIUS has the file locked.  It never closes the file after save.