Disappearing autogen

Hello again,

As usaul another problem. I design in FSDSV2 and install with FSSC,in FS9.I have the Misty Moorings addon scenery and designed a small scenery,1.92MB. I added smoke in two places and couldn't get the game to boot, I removed the smoke and it works. Now if I take off and return to the same place, the autogen tree's are gone. The only way to get them back is to restart the game. I have no clue as to why this happens. I've done bigger scenery's in the past with smoke, lights,etc. and haven't had this problem. Any help will be appreciated.