With advancements only items in tabs are affected.

The achievement menu still renders items differently than anywhere else, major issue that it sometimes renders custom models in the improper order in some cases (depending on rotation). Sometimes elements that shouldn't be INSIDE other elements will render as if they're BEHIND the element they should be inside of.

The rendering, at least in 15w32c, seems to be much more dependent on rotation than it previously was. A very repeatable way to cause the issue is to use the render setting

"rotation": [ 10, -75, 60]

on any (somewhat advanced, or at least has possibility of messing up) item model that happens to be in the achievements GUI.

Related to MC-36772 and MC-36716 any enchanted golden apple custom model renders as if it's partially transparent (the glint making inner parts of the model visible) , likely because of the glint.

Previously, models rendered incorrectly in the statistics menu, but that appears to have been fixed without this. The achievements menu should be using the same rendering code as the inventory GUI, if possible.

Related to MC-33065 in that both of these are issues with the achievement GUI rendering items. Also, the lighting changing based on what item you have in your hand can change how broken some custom models look.

EDIT: I'm not sure if any other tickets mention it, but animations no longer work in the achievements (background or icons) or statistics menu, while animations used to work there perfectly.