I'd have to ask Vin or Jason to be absolutely sure but I believe it has to do with "bones", which is a concept used in designing skinned animations on the models. Without the option on, the bones aren't drawn and that's why you see the effect in the OPs screenshot.

Yes.. advanced animations are basically animations where individual vertices of the model are linked to specific bones, with specific weights. In simpler terms, it's the way you might animate a rubber hose to bend, without having to cut it up into individual segments.

:( I have a picture in my head where the whole PMDG crew sits around a table starring at a computer screen... for some minutes nothing happens and then anybody says: "why is it doing this?" -"no idea":(

And now that picture is stuck in my head.. haha, thanks