Can anyone tell me why the steps on my staircase are not coming out level? (in any direction/Plane)

The spline that I am using comes from an intersection that holds the main curve, and the gradient.

I can't seem to understand where Solidworks could create a gradual slope on a linear pattern when there's nothing that is twisted in that manner...

Thanks

Can anyone help me? I'm still stuck and I can't seem to figure out what is driving this twist in the step...