The Import3D tool
NEURON Main Menu / Tools / Miscellaneous / Import3D
offers several methods for trying to automatically repair z axis artifacts. After importing the morphology file, click on the "Show Points" button to eliminate all the blue boxes, then click on "Rotate 45deg about y axis" twice to get a side view. Next click on Import3D's "Edit" button for a panel of buttons that allow you to select from a menu of strategies for dealing with z axis errors.
That said, I wouldn't waste my time on such data. First problem is: how can you tell that any particular point is affected? Set a threshold for z axis jumps? Risks false negatives (missing artifactual jumps that are less than the threshold) and false positives (neurite trajectories that genuinely deviate from the xy plane may be mistaken for a series of artifactual jumps). Even if you can accurately identify artifactual jumps, what do you do to fix them? Reduce delta z at each affected point to 0? Infer delta z from the delta z values of neighboring points, e.g. by linear interpolation or spline, or probability distribution, or 3 point median filter? Why deliberately use data that one knows is faulty and cannot be fixed in a way that is "guaranteed" to work?