ORIGINAL: wphilb
Turned out that the wires, under load were allowing a differential twist on the wings. We tighten the wires carefully again at home under simulated flight loads and that fixed the issue.
That's an interesting point. A wing without wires will (one would assume) flex equally. However, one you add functional rigging, slight differences in the tensions of the wires might allow the flex (and there's always flex even with wires) to be unequal. I had what appeared to be a "twisted wing" problem with my SE5 even though the incidences as measured in the shop were dead-on perfect.