Changing the resolution of the image is a bit annoying, cos the size of the preview windows does not change automatically.
Simply right-click on the image an select "100%", this should solve it :-)
If you max out the dimensions to 1920 (=max) x 1040 pixels, no stripes will show up.
When going above the 1040 pixels in Height, stripes will appear.
Be sure to right-click the spectrum after altering & hit 100%.