Incorrectly low scaling on sprite bumped normal maps

I'm having an issue with applying normal maps to my sprite: the scaling of the normals is done far too low, around 20% of what it should be. You can see different normals from the same sprite sheet applying to a single animation frame here:

What's going on is that different frames from the normal map sprite sheet are being represented on the single still image, so different parts of the sprite are getting the normals from different animations, scaled down.

Here are the settings currently used for the normal map, material, and sprite sheet, respectively:

This mis-mapping applies to most shaders I've found for bumped diffuse lighting on sprites. The current shader I'm using is this solution, but I think the issue is more likely related to an import setting as others seem to have little problems with these shaders.