Topological flatness of orthogonal spin local models

Let $p$ be an odd prime and $F$ be a complete discretely valued field with residue field of characteristic $p$. For any parahoric level structure of the split even orthogonal similitude group ${\mathrm{GO}}_{2n}$ over $F$, we prove a preliminary form of the Pappas-Rapoport flatness conjecture: the associated spin local model is topologically flat.