Can anyone help me with the proper usage of a tangent space normal and the gradient bump connection?

I'm testing a product (unreleased, hence no screenshots) which uses normal maps plugged into gradient_bump. They're set to tangent space and 0.5. The figure looks horrible and splotchy if I leave hardware shading on. The texture only looks normal if I either turn hardware shading off, or change gradient_bump to 1.0.

I always leave hardware shading on, but I've never ran into this issue. Is the proper solution to turn off hardware shading, or to change the texture's gradient_bump to 1.0? Or is this a bug altogether?

I'm using PP2014 Game Dev SR5 and set to inches.

/edit

Gamma on the normal is 1.0.

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Daz, Blender, Affinity, Substance, Unity, Python, C#