You don't mention your end goal, but for this object at least, it seems it might be simpler to just create it with a GN setup in an empty mesh like below:
This produces a curve as pictured here with no artifacts:
Problems like this are usually going from bad topology.
So first of all, I turn on "wireframe" in "viewport display".
And i see that this is a crease. Faces are extremly scaled in the direction across curve. In other words there are too much cuts along curve. So the solution is to reduce number of cuts along curve. That is why you should ...