In the Russian 5 course, level 16: Terrestrial Weather, the number of words shown as total is 28, but the level only teaches 27 words.
This makes it impossible to complete the skill, as it’s always showing that 1 word is left to learn.
When clicking the “Continue Learning” button, the error “Could not load session. Sorry.” is shown.
The same thing happens in the Android app.
A similar bug is reported here, but the Russian course hasn’t been modified lately.