This cant be reproduced in the vanilla Orca HUD (which afaik is the only vanilla HUD which uses this feature so far) but I have a simple HUD setup which can be used to detect the problem.
here's a pastebin for class AirplaneHUD (basically all it has is a very long horizon line attached to the Forward Vector and Horizon bones, plus some random debug stuff to help visualize.
http://pastebin.com/3aNtxNJJ