I am using a 3600x1800 environment texture to cast reflections on a completely reflective sphere, but all the reflections show up in very low resolution. If I turn on "Rendered Viewport Shading" and pan around I can see the background as having the correct high resolution.
What do I need to do to get the reflections to show properly?
Update: after both increasing the resolution and turning on smooth shading on the sphere, as was suggested in the linked answer and comments, I was able to get the desired result.

