UE4 has support for real-time Planar Reflection that can give more accurate looking reflections than Screen Space Reflections (SSR) provide but come with a higher rendering cost. This higher rendering cost is due to how Planar Reflection works, as Planar Reflection actually renders the level again from the direction of the reflection.
This was what I was going to suggest - render the same object twice with the second one flipped according to the angle. I am glad to see that the engine now has something built-in to do that for us at a lower level (likely a much more optimized solution as well).