I consistently experience (over a period of several weeks) occasional crashes.

If it makes you feel any better, I experience it several times a day…

on Monday it got to a point that I took several days (three and counting) break from Pharo because I was so utterly frustrated by this…

My rough observation is that this happens when working with visualization.

Do I do something wrong, or are there some issues?

There are (at least) three different crashes that happen often… two related to Athens/Roassal it seems (one you reported is one of them) and one related to fonts.

Of course I reported all of them, but with no known way to reproducibly crash it, I seriously doubt it will be fixed anytime soon.