Beachy Head Under Moonlight F5.6 @ 1 Min - vertical banding on scanned image

The grain seems to actually enhance the image, but, alas, you need to agitate better: the negative shows ugly 'vertical bromide drag' on the water and sky. Using the Planar to enhance this is, in and of itself, a 'drag'. I really wonder whether those negatives are a clean as you propose. Seeing this 'drag' is difficult unless you are looking at the right light angle. I could be wrong, but I will opt for deficient negative agitation as the culprit. Maybe, however, the digital gremlins are at fault. - David Lyga

Well it's a good scanner so hard to tell what is causing it. Have you had this issue on other images?

The image itself is gorgeous, try rescanning with the negative turned 90 degrees...

Thanks to all for the responses.
I have just re-scanned the negative at 90 degrees as Reinhold suggested and it has fixed the problem! Many thanks Reinhold you are a genius! Now I need to understand what is going on with this scanner and these particular negatives. Tomorrow I will clean it up and post it here together with the 4x5 I took that evening.