https://bugzilla.kernel.org/show_bug.cgi?id=213391
--- Comment #12 from dimitris@gmail.com --- Hi, I've seen this under 5.12.10-200.fc33.x86_64, two incidents hours apart. Earlier had a number of incidents under 5.12.9.
In all of my cases I was using Firefox "heavily". Creating tabs and using graphics-heavy pages.