(URP) Phantom cascades from cameras

What's happening
Two cascades of shadow appear toward the bottom of the camera view. See the screenshot, where I've roughly shaded the cascades in case they're hard to see. The effect occurs in both the view of the main camera and the editor camera itself and moves with them. The closer the camera is to the terrain, the larger the cascades are. The issue appears similar to those referenced here. My project is using 2020.3.5f1 (the issue isn't unique to this version) and the URP.

What I've tried

• Deleting and recreating the directional light
• Tweaking all the options on the directional light (e.g. bias), on the Universal Render Pipeline Asset (e.g. Max Distance and cascade stuff), and in the Lighting window (e.g. Skybox Material)

Nothing I've tried appears to make any difference. The effect even survives the disabling of shadows on the URPA and on the directional light! As I'm not sure what else I can do, any suggestions would be greatly appreciated. Thank you!

 

It's something to do with the normal map on the Terrain Layer receiving the "shadows." If I remove the map, the problem goes away. Curious!