Hi,
Same problems here. It was fine Monday 7/30/2018 morning (Europe) on my Windows laptop, but when I worked later in the evening (Europe; US afternoon) the same day on my Mac laptop, the same problems started.
I tried it today again on my Windows laptop and it is the same.
All left area - console and markup file - have a gray background. I can select something in the console and it is highlighted. I can select something in the markup file above, but nothing is highlighted. However, something is invisibly marked. I can drag & drop text with my markup file. I just don't see what I drag.
This in annoying!!