Banding: rounding error, not slit issue?

[vnp85]

Using my Sodium images, I extracted two adjacent pixel offsets, separated by 0.5 pixels. The result is a reversal of the banding as shown in the pictures. Hence, my working hypothesis regarding both INTI and JSol'Ex is that at least some of the banding is a result not of the slit but of the disk-to-pixel mapping, falling sometimes towards the edge of the spectral line. This issue may then be exacerbated as the mu angle (together with the bending of the line's projection) increases. It could also be a camera readout issue, as the pixel shifts traverse camera scanlines at different x coordinates.

[outputs]
diskM0p5 = rotate_rad(img(-0.5), angleP)
diskM1p0 = rotate_rad(img(-1), angleP)
diskM1p5 = rotate_rad(img(-1.5), angleP)

diskP0p5 = rotate_rad(img(0.5), angleP)
diskP1p0 = rotate_rad(img(1), angleP)
diskP1p5 = rotate_rad(img(1.5), angleP)

diskM0p5LS = linear_stretch(rotate_rad(img(-0.5), angleP))
diskM1p0LS = linear_stretch(rotate_rad(img(-1), angleP))
diskM1p5LS = linear_stretch(rotate_rad(img(-1.5), angleP))

diskP0p5LS = linear_stretch(rotate_rad(img(0.5), angleP))
diskP1p0LS = linear_stretch(rotate_rad(img(1), angleP))
diskP1p5LS = linear_stretch(rotate_rad(img(1.5), angleP))

From M1p0LS and M1p5LS we have the following two frames, which shows the banding "blinking" ie getting reversed: