as I have spelled it out above, by “flashing” I mean that the background image I added via “Customize Style” > “Website Background” is briefly visible each time I navigate to another page and BEFORE the loader appears. I solved this by using a very low resolution background image – which stopped the flashing, at least on my machine. I wonder if this theme loads its assets once – or again and again and again…?
Second problem was the uncomfortable “jumping” of the background image, due to the scroll bar, each time a new page is called. Solution for this is: