There are a few Hang Gliders such as the one in Banapur that are next to a tree. You can't fly it period. Every time you get on, it snags the tree it is placed next to before you even have any chance to control the glider. This happens with the 1.5.0 PC patch. I don't recall this happening prior. I found 2 glider spots like this so far. It also does not appear that the "up" key binding for the glider was fixed. You can go down, but not up.