"Review Forecast" empty on small Android phone

For a while now, “More Stats”/“Review Forecast” has been empty for me (no bars, no labels) when I look at it in Firefox on a small Android phone. However, it behaves normally in Firefox on a larger Android phone and on Windows. Another odd thing about the display on the small Android phone is that it shows an additional instance of the words “More Stats” in the center top of the display area, but this goes away when I press it.

This problem seems to be sporadic. Last night, I was able to see the bars and labels on my phone. But this morning, I once again was unable to see them there. I’ve always been able to see them on my desktop.