Can somebody explain what's happening?

Did you use a Multi-Section Surface to make the wing?

Double click on the surface and look closely at the inputs. Make sure all you have all the sections correct, with good starting points. Are all the arrows pointing in the same direction? Did you add tangency or curvature continuity? Are those good.

What about the splines you used for sections: Are they good? Did you analyze them for smoothness? (porcupine analysis)

Looks like the wing surfaces are not very good. Could be many reasons why; some of the most-common are:
- bad curves (not smooth) used for surface definition
- not using guide curves
- not applying proper continuity definition to the surfaces
- not enough sections in the lofted surfaces, or too many sections
- not taking the time or effort to design good, smooth surfaces
- etc.

Use CAtia surface design platform instead of doing multi-section, loft or swift command.