Blog / Blog Post Menu Issues with WP Sites

I have two websites that have the same issue. From time to time something happens with the blog: either the blog page itself gets menu ?in the header corrupted, or one of the blog posts gets menu corrupted. I recreate them from scratch and they are fine again (that’s what I have done now).

It seems to be happening after automatic updates, though I can’t figure out which one: once it happened after Classic Editor Plugin update, another time – after JetPack plugin update.

Both sites use Inspiro theme (I love this theme very much!); theme support say it’s not a theme-related issue; hosting provider has not been able to find any issues.

Are there any ideas how to fix it?…

Thanks.

The page I need help with: [log in to see the link]