[Решено] Menus not visible in French version of the site

Background of the issue:
I've noticed issues with the visibility of French menus in the 'Appearance>menus' section of my WordPress site using WPML.

Symptoms:
Sometimes the French menus do not appear and the page shows up blank. If I revisit the page later, the menus reappear. During the times when the menus aren't visible, I am unable to create a new French menu.

Questions:
Why do the French menus sometimes not appear in the 'Appearance>menus' section?
What steps can I take to consistently display the French menus without them disappearing?