It seems the Destruction Brush save function has become broken at some point (at least as far back as 4.13.4). I can’t find any previous discussion on this though, so it is probably a fairly recent bug.
On various maps many of the brushed destruction tiles will change to bright red when the mission is saved/played in the FMB, or even instantly while brushing another area according to Beebop! This is not just a colour change, the level of destruction physically changes by itself!
For more details please refer to this discussion on M4T.
http://www.mission4today.com/index.p...wtopic&t=24458