Try using Window>>Histogram in Wilbur. You'll probably find that there are a few (perhaps one or two) points that are very large or very small and that most of the rest of the points occupy a narrow band around 0. This kind of data causes Wilbur's auto-scaling to become confused. Use Filter>>Height Clip only leave the altitudes close to that middle band.

The data errors happen because some versions of FT can generate bad data in response to certain operations. These values tend to end up in the hidden last column of the FT data. Using Tools>>Actions>>Normalize Data in FT can sometimes fix this problem.