That fork exhibits quite a bit of rake, I would not call it shallow, but considerable. might be an interesting investigation to measure the trail as built, how far behind is the tire contact patch center from the virtual extension of the steering axis as it hits the ground. If it is under 50mm that is why the bike might feel unstable or "darty" Contrary to initial thought, less rake might be more stable in this case.

The bike is handsome, by the way.

Also, does the wheel feel like it "flops" coming out of a turn?