I circumvented both issues(destroyed-or-departed-delay and message coming from a string variable)with tricks.
There's something I can't circumvent: there's one mission that, apparently, shouldn't give problems. FRED doesn't report errors. I select the mission with the simulator. CB is ok, briefing is ok, I select commit...and after a few seconds FS Open crashes(the mission doesn't start, there still is the briefing interface during the crash). No errors are reported.
It's Sol1-09a, you should be able to get it in INFA internal(Woo's thread, 2-3 pages behind the last one).