What is this circular icon? 1/3 blue 2/3 gray

Hi, I’m animating with Toon Boom Harmony and this strange icon appeared in the center of my screen. It doesn’t render but I can’t seem to make it go away while I work. It’s pretty distracting — a small gray circle with 1/3 highlighted blue, like a pie slice. Please help me get rid of it!

The “pie slice” looks like a clock that is 3/4 of the way through a cycle.

Is it there in all project files or just this one?

Does it appear only when in animate mode?

Have you tried saving the project under a different name and re-opening it?

Have you tried Preview mode or adjusting OpenGL preferences?

Is your graphics card up to the task of running Harmony?

Just this one, I’m not sure what I did to make it appear.
I went to work on it today and it’s disappeared, so that’s good! But I’d still like to know what it was.