So to answer some of your questions in-order.
I definitely tried experimenting with just basic foliage meshes (such as a single grass mesh and cubes & cones), that did nothing because it didn’t seem like the amount of foliage or grass types were affecting it.
To reiterate my problem, adding a procedural foliage volume removed all of the grass, which was spawned from the landscape material, from my level tile. Before adding a procedural foliage volume I can package the build and the grass appears without issue.
I am using LODs, the shadows are just whatever the default values are, I haven’t played with those settings yet.
I am using world composition, the tiles all exist in the same Persistent Level. I used the “Import tiled landscape” feature in World Composition so the setup of the tiles was all automatic.