Another approach, first look at the graph to see where the hip rises and the pattern of the curves and peaks, use the script, then in the hip's Y paramater graph highlite the section of keys where the jump is, delete the the keyframes and set new keyframes to remake the jump with a similar curve.

If an animation progressively sinks below ground, as sometimes happens in bvh files, this can be fixed using straight splines on the Body's Y trans, again refer to the hip y graph to see where you need to add keys.