Procedural Mesh Component leaves invisible collision behind. (UE4.27.2)

When I update the mesh (using CreateMeshSection_LinearColor, build collision true) it leaves some invisible collision behind, in previous positions. It only happens if you enable bUseAsyncCooking. I’ve tried lots of things, including calling ClearPhysicsMeshes() and InvalidatePhysicsData() on the ProcMeshBodySetup before I send the next stream of verts, but nothing seems to fix it. Just wondered if anyone knew how to fix it. Thanks.