Compute shader Works on Intel but NOT Nvidia

Hello,

Im running a compute shader to generate a coarse intensity grid for a volumetric MRI, however the results on Nvidia are incorrect compared to Intel Integrated GPU. Does anyone know why this might be?

Intel Result:

Nvidia:

Skull_Intensity_Nvidia

The shader is alliable here:
https://pastebin.com/ZxzxfiCR