I made a new project and imported the meshes and took a screenshot of everything that I did:
I created a BP for the shelf, added a mesh and set the cupboard as the static mesh. Created a simple material for it, and just to check I used the master material, not an instance of it on the mesh. (later checked with mat instance, no difference). Dragged 100 of them on the level and checked the empty shelf drawcalls. It wasnt good.
Then I created a potion BP, and programmed the shelf to spawn 4 potions on the shelves at Beginplay. I created a blue material instance for it. The results were the same as in my other projects. Huge drawcalls, low fps.
I guess you made a new project to test my problem out, and I did as well but failed. I didn’t tick, change, or set anyting in the starter scene or in the blueprints when I made them. Just the ones I screenshotted. Is it something basic I don’t change when creating them? Maybe its a setting in the Project Settings or in a component?