Comment 2 for bug 1934996

The blue lines are the grid in the preview display. Deactivate the grid in the view menu and the "blue lines" are gone.

The problem with the generated panorama are the control points: there is only a single control point between image 5 and 6. Also other image pairs have only 2 control points. Other images pairs have about 20 control points. I don't know how you come here. Tested with your images cpfind find enough cp for generation of the pano.
There is a small issue with a wrong detected vertical line control point. Remove the line control point from image 7.

What worked for me the test images (from scratch):
1.) Disable finding line control point in preferences, assistant tab
2.) Load images…
3.) Press Align…