I noticed the marmoset viewer seems to use 8-bit normals, which can cause a lot of artifacts going from 16+ to 8. But you only have a shot of the issue, not of your mesh, not of your bake, not of the high or low, or wireframe. We're gonna need more to help.
It's hard to tell from the image, but it looks like it may be z-fighting. If you have two faces that are very close to each other, try moving them further apart.
If that doesn't solve it, please email support@marmoset.co with more information about the problem.
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If that doesn't solve it, please email support@marmoset.co with more information about the problem.