Vertical dotted line appearing on Macbook Pro screen in Finder

Hi, I have MacBook Pro (Retina 15", Mid 2015, 2.2GHz Intel Core i7, 16GB Ram, 256 GB storage) and a day after Mojave update (From HighSierra) I start to notice high contrast vertical lines appearing in Finder (dividing line between sidebar and main window - in list view). See attached photo.

It is not through the entire screen, and it disappear after a few scrolls or reopening Finder windows - sometimes the lines fade away quick, sometimes the lines flash a bit and then fade away.

Anybody has explanation for this? TNX!