I saw a tip to add the tilemap images to a Sprite Atlas; I did that, but it did not impact the visual distortion.
Just to clarify – these distortions are not part of the tile itself. They appear and disappear seemingly at random as the character (and the camera) move around the scene.
This is either a problem with your tilemap since it might not tile correctly or has a small gap, a problem with the settings (anti-aliasing, anisotropic textures), a problem with your camera’s resolution, or missing padding. If padding is missing the Sprite Atlas 100% fixes this. But it only does so in-game. In the Scene view you will always have these seems.
Ah! I think I’ve solved it. The issue was that I wasn’t using power of 2 textures. I changed my sprites from 500x500 to 512x512 and the issue seems to be resolved.