This has to take the trophy for my favorite bug report 
In seriousness though I think @TheSevenflyer is onto something. If the detrimental effects of icing on an aircraft is programmed, for example, as a “negative value of lift” of lift that is activated when icing=true, then when the aircraft is inverted, up becomes down and down becomes up and the aircraft nosedives into the sky.
I wish icing worked like this in real life. Then we would design aircraft with invertable cabins and intentionally fly into known icing for free lift and better fuel economy.