try increasing the mesh distant field resolution of the sink in the mesh editor see if this gets rid of the artifacts. note that this only effects the lumen reflections.
the artifacts in faucet in the raytraced Lumen reflection or the hit lighting method are because the reflection of a reflection only works in screen space so you get these black spots.
the only method to avoid these limitations is to use hardware raytracing or standalone ray traced (deprecated) in the PPV and that also has its own problems because while the reflections are sharp and accurate it does not reflect the GI of the scene so looks weird especially for interiors .