Fix Woocommerce problem after upgrading to PHP 8: the menus just disappear from the frontend and the backend

Hello, I am looking someone who can fix a problem I am facing with my Woocommerce shop. I had just the shop working properly, but after upgrading PHP version to PHP 8 one problem started to appear. I had many menus with lots of items within them, but now the items just disappear. The menus seem to be empty, but when I add some item to a single menu and I click save, the lost items just appear again. However, some time after, the items do disappear again. I attach an example of the menus in GIF format.