OK, so I've got a mission that has you flying escort for two Argos. Pretty much perfect, except for one thing - FS2 is sometimes failing to pick up if the Argos get disabled. At first, it was just affecting Argo 2, and I couldn't work out why the event wasn't firing. I tried substituting 'subsytem-destroyed-engines' for -is-diasbled', and similar stuff, but no joy. When I checked the events log, I realised that FS2 seemed to have not noticed that the ship was disabled, even though it was quite blatantly sat there with 0% engines and a 'D' next to its name. Argo 1 was behaving, and if it was disabled the appropriate event would fire.
Since I had the mission in a campaign, I took it out and flew it from the tech room, and it seemed to work fine. So I put it into a new campaign file, and still it worked OK. Then, without me touching the fc2, it went all wrong again. If that wasn't enough, the disease seems to have spread to Argo 1, and neither of them showed up as disabled.
As the old saying goes,

Any ideas?