Ok, got it, one of your curves is messed up. I duplicted the problem curve and moved it forward to show how the CVs look when moved. This curve is actually a closed loop that originates in the middle.

The good news the other curve is fine. Delete problem curve, dup the good curve, then loft with duplicated curve.

Tip: Learn to identify curve directions. The first CV of a curve is indicated by a square, the second is "U" shaped (indicated the line "U" direction). On the good curve you'll notice these indicators at one end of the curve. On the bad curve the are in the middle of curve.