Does Facebook sometimes block the ability to search for private messages?

Question

It seems Facebook completely dropped my support (but not for other people I know) for searching for messages. I can only look for conversation names (persons, pages or chat group names) or search for messages inside a specific chat.

This directly contradicts what Facebook's official support states, and as mentioned it does work for other people. It doesn't work for me in any browser.

Any idea what causes this and how to fix it?

This is how it looks like now:

If I choose a specific chat, I can search by clicking "Customize Chat" first, although what does search have anything to do with customization? It's as if they don't want people to know search is possible within a specific chat:

And this is how they (used to?) search text in all previous conversations:

Answer 1

And just like that, searching for content in all messages is back.

Did they run an experiment on me (and on @Darryn Brisdaz from the comments)? All I know is since it took them months to give it back to me, I mostly stopped using Facebook and I will never write private messages there again unless I have to. I realize they couldn't care less about a single individual, but that's what happens.