Okay. There are a large number of missions (and I mean LARGE) FREDded. The problem is not with the missions per se, but the gameplay design.
The missions are long. They are often a bit repetitive. And, unfortunately, it is really really easy to get killed by a circle-strafing Kestrel. This makes testing them onerous and unpleasant, which in turn means the missions have not been iterated properly.