First attempt at mission creation. Getting huge frame drops on gaz down to 5fps, but not hind or other helos?

[S. Low]

I'm not sure if the track will show it or not. At the end of the track I've dropped from 70fps to 5fps. Sometimes it happens on the gaz when I start, other times it waits a few moments. I don't even know where to begin with this. I swapped the gaz with the hind and the hind ran fine. So is this a gaz bug? A mission editor bug? Or have I screwed up some logic that is causing a serious issue? 

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