sounds to me like you have a laminar bubble warbling back and forth on
the aerofoil. some bubble trips might be in order to nail that little
puppy down and make the ride more stable.

you also realise that Old Warden has a flying vintage aircraft from
that era that can only be successfully flown at a single airspeed.


Yep,
This is both a center of pressure issue and an AOA stall issue. They
knew about it and finally saw it appear in the metrics from the wind
tunnel 2 years later. Of course they didn't know it was a "bubble",
they just knew that the C.P. moved in mysterious ways as the AOA was
changed, and lift did not build linearly. The airfoil used in the 1899
kite is a flattened parabolic curve, similar to what Chanute, Herring,
Avery, & Huffaker, et al. were using. This changed to a modified
Plin's curve for 1900 and 1901, and then changed again to the Wright
#12 following the wind tunnel tests.

Harry