Generated mesh render order

Depending on the viewing angle, these runtime-generated Meshes (floorboards for a treehouse - just for reference), will render in the wrong order, resulting in faces that should be occluded being rendered on top. I've attached two images, one features the bad render order, the other (from a slightly different angle, where the problem stops) shows the intended result.

Normals are good, and I call RecalculateBounds() when I'm done modifying the Mesh data. Each floorboard Mesh is attached to a separate GameObject + MeshFilter + MeshRenderer.

Wondering if anyone has any recommendations.