Wrong line spacing

Greetings all.

After my company laptop was souped-up with Win10, I got a squeaky fresh install of Storlyline360.

Now, to my surprise, the line spacing in all the pages of the lesson I was working on seems to have gone 'back to basic'. In other words: way too cramped (see attachment 'wronglineheight-14to16.jpg').
Although the line-height is set correctly (font-size 14pt and line-spacing (exactly) 16pt) it still doesn't display it correctly.

I had a look at a previously made lesson (with the same setting of font-size and line-spacing), and that is the way it should look (see attachment 'correct-lineheight-14to16.jpg').

I checked the text size of my browser and my OS: they are both 100%.

How can I make the line-spacing behave correctly?

Regards,

Marcel