I just went through something similar while making my own custom ground materials. Might be that the source Normal that was used in the COMP/NRM was not in DirectX format? Or the wrong source channel was used? If that’s the case then the Alpha channel colors may just need to be inverted.
In my case I was using the Normal’s Blue channel in the NRM Alpha instead of the Green channel, as I misunderstood the SDK. For the Normal I though it was:
R = X
G = Y
B = Z
But it’s actually:
R = X
G = Z
B = Y