There there,
You have to learn the feel the kite. Forget looking at it. Feeeeeeel it. Let the energy course through you, tune into it, use the force.
Sheeted just right strutless kites really don't flap much.
They are pretty easy to make flap, but its still rider error. The longer you ride them, the better you get at it.... Unless your out in too much wind for the size kite your on.... then your simply overpowered and that is that.
Short lines help loads to mitigate flapping.