That's a known issue, and it's not something we can't do much about it.
We draw scenery buildings in C++ with Simconnect, without using the BGL format.
This gives us a lot more options for fps optization, because we can precisely control the loading distances, visibility distance, disappearance over a certain height on ground, complexity settings, conditional display depending on seasons, time of the day or week. And, we don't suffer from the loss of LOD that plagues all other sceneries, with the appearance of the FSX SP2 (all BGL objects always displays at the highest LOD in FSX SP2, regardless of the distance).
That's one of the reasons why we are able to offer highly complex/big airports that many thought of not being possible in FSX.
The side effect of this, is that those objects don't appear in Instant Replay, which is probably related to how Simconnect works.
I think the advantadges far outweight this minor annoyance and, there's always the chance to use FSRecorder (
http://www.fs-recorder.net/ ) , if one would like to have better control about replays. This is confirmed to work without any problem with our sceneries.