The vertical lines you see are common defects of the CCD chip, called "bad columns" that cannot be removed with calibration, but only in post-processing during stacking or through interpolation. These are just columns of pixels that do not work properly.
Columns defects are an inherent problem of the manufacturing of high-end CCD chips, like the one used in some of our cameras (KAF 16803). There are multiple reasons for a column to be bad, from electronic to mechanics. In some cases, the columns are completely dead (dark), and cannot, therefore, be fixed in the calibration stage. In many cases, these columns have some constant added to what they should normally show, and can therefore be fixed during calibration. A good CCD usually has no more than a couple of them. All of our CCDs either show zero or up to 2 columns.
You can watch the tutorial by Alex on how to remove these white lines using PixInsight. Click here to watch the tutorial Cosmetic Correction in Pixinsight.