I'm unable to create a reasonable pano from your A & B source files. A few things are obvious:

• The nodal point is off as evidenced by the plants in the foreground and the railing. It looks like a lateral translation between images.
• The clouds are moving between the shots which will cause blending issues.

One thing I can't get a grasp on is why Hugin doesn't calculate lens distortion parameters on the A & B images. This is paramount in creating a good panorama. Perhaps due to the varying camera position.

When taking panoramas, a few rules:

• Use a tripod. If possible align the camera on the tripod with the no-parallax point (often called the nodal point, but really the entrance pupil). Aligning the camera at the nodal point requires a special adapter.
• If you don't have objects close to the camera, you can successfully create good panoramas without proper nodal point alignment. This looks like you held the camera at arms length and rotated about the axis of your body creating large shifts in the camera position. There are many tutorials on the Internet discussing how to shoot a pano and probably many posts on StackEx.
• If you don't have a tripod, you can take a hand-held series of shots if your body is stable (lean against something so your body doesn't wobble). Use your finger as an axis point near the nodal point of the lens and rotate the camera about the axis point. Try to keep the axis point (your finger) as stable as possible.
• Use manual focus and exposure. Do not change focal length between shots.
• When creating the panorama, eliminate control points on clouds and plants (wind tends to make plants move).
• Practice using a simpler subject matter where you have good lighting and a stable subject matter (no clouds or plant matter that moves in the wind). Having object(s) near to you will tell you if you are rotating the camera about the nodal point.