Nanite was the issue for me as well. I was trying to dynamically scale my foliage in a material, but the ObjectPosition node gives the nanite group’s position, not the individual foliage instance. It was working for other foliage, since I forgot I’d experimentally turned nanite on for this foliage type’s mesh 
Here’s my shader graph, for anyone curious
In my case, I simply disabled nanite, since I wasn’t using it intentionally. If there’s a way to get this form of material-based scaling to work with nanite foliage, I don’t know what it is.