@hwpixo I encountered the same issue with 5.4 nDisplay, affecting not only Nanite meshes but non-Nanite meshes as well.
During my testing, I noticed a couple of things: when I selected meshes that weren’t visible in the inner frustum, hiding and then unhiding them in the editor viewport made them appear. I also toggled the “eye” icon on and off in the outliner, which caused the meshes to reappear as well.
Additionally, once the meshes reappeared in the inner frustum, it didn’t affect the level snapshot when switching to another scene state.
However, it’s frustrating to have to go through this process every time I launch it on Switchboard, and it seems like this is just a temporary fix. As you mentioned, this could likely be a bug in 5.4.