It is possible that you are fooling yourself about any twist in the surfaces. One way I tell is to look at the surface from some significant distance behind it, looking at the trailing edge. If you shift your position so that the line of the trailing edge intersects the "horizon line" of the control surface at about at the thickest point, you can tell if the trailing edge is parallel to the horizon line.
Another possibility to suggest, and bear in mind I am not very familiar with the -14 kit assembly, would be if the flap hinges were mounted to the wing a little too far forward. This would have the effect of deflecting the flap downward a little when the flap leading edge rests on the drag spar. It would only take a 1/16" shift in the flap hinge point to move the flap trailing edge down 1/4".
"The Magic Carpet"
also LS-6-15/18 sailplane
VAF donation Jan 2019