Certain models do not work and display as the default model. As far as I can tell, it only affects models that contain an element with custom rotation. I tested these models in 1.8.8 and 15w44b and they work fine, but in snapshots 15w45a and all snapshots after they are broken. The first image is taken in 15w44b, the second in 15w47b. (The first image is meant to have a broken texture when seen from this side, because in my map it is not meant to be seen from this side. I took the screenshot from this side to better show that the model has not taken effect in the second shot)