[Closed] Posts and pages disappearing

I have a multisite with some subsites. In August the person who run the Finnish site told me that pages had disappeared from her site:
"while prepering one presentation where I wanted to link to the Finnish CORE subsite, I noticed it is totally empty! So, there was content only on the main home page, but all other page links said that the page does not exist, and there was nothing under the measures, publications, blog etc..

I have no idea what has happened, as I have not touched the page for some time. The other subsites seemed to work normally. I think I managed to recover all other things besides the blog. There was only one post by me, but I cannot find it anymore. And also, when you enter some other page from the homepage, the link "Home" disappears from the bar, so you cannot get back there anymore.

Can you have a look at the page? Hopefully you can fix it.. It makes me a little bit worried about sharing the links and promoting the page, as I think this is the second time it crushes, and one time the content had updated itself to the automatic translations.. "

I couldn't help and we agreed she would recreate a simpler (tiny) subsite. As far as I can today that is still there. Then the person who runs the Spanish subsite contacted me:
"the post of the Spanish subsitio dissapeared. There were 10 posts and now only showing 3. IN the dashborad of WordPress say that there are 10 posts, but also there I have the Access for only three post (by the way those are the first three posts that I uploaded). I was looking for the posts everywhere, but it is imposible"

I was on leave so I forwarded to my very good ISP who said:
"Looking at the site data, I suspect part of the problem here may be that you have quite a few things in weird states from the WPML (WordPress Multilingual, previously known as 'sitepress-multilingual-cms') plugin, and which itself may need updates.

Most notably, there's hidden link, which is the main English site, with various other sites like hidden link under that, but at least some of the content (like hidden link) is actually on the main site.

As it's seemingly related to the translated content, it's most likely the WPML plugins support methods will be the best option to resolve this as they'll be aware of any compatibility issues with other plugins."

Now when I look at the site in the admin pages as global owner/administrator in the main site it says there are no posts (but if I look as a visitor there are 15 and all are accessible with none missing). If I look at the Spanish subsite it shows me this image which says there are 11 posts and four in Spanish. This seems to suggest that the posts database is corrupted removing 15 posts from the main site admin interface but preserving their content for visitors and it has lost posts from the Spanish subsite and, earlier, posts and pages from the Finnish subsite.

This is obviously extremely worrying. I have provided the debug information and can give you administrator access to the site if that's useful. I hope you have some ideas about what may be happening.