AFAIK mesh instances using WPO are still not supported. It’s very hard problem to solve, in both offline and realtime rendering. So if you have your mesh instances animated by WPO (shader effect), then the shadow maps are generated for static version of the mesh, in original pose without WPO, and then applied to moving mesh. This causes shadow map to randomly intersect through the animated meshes, making shadows appear sometimes in front, sometimes in back of the mesh.