Review all items doesn't work for some courses (Italian)

When I go to “Review all items” in the Italian category, I get an error: “For some reason your Review session couldn’t load. Why not go back to the dashboard, learn a few more items and try again?” What happens is that some of my courses don’t work under “Review all items” but they are fine if I open them up separately. However, this time I opened the page for every course and didn’t see any that had words to review.

I’m using Firefox on a desktop computer.