For some time (maybe a recent update), the screen has been breaking down into a mosaic when I am scrolling through a notebook.
I tried the same with a regular script but it only occurs in Markdown.
I got lucky to get a screenshot.
I thought it was an issue with the HDMI cable or my external display but it also occurs on my computer when after unplugging the cable and the screen.
Have you tried changing to software rendering?, you can change it by holding the Ctrl key while opening RStudio, then you should see this menu and change the "Rendering Engine" to "Software".