Database error – tags are not being displayed, but they exist

Hi.

I’m having the following issue.
Whenever WordPress try to get any term from database (product_tag, portfolio_tag, etc) I see messages like:

WordPress database error: [Error writing file '/tmp/MYAD3IY1' (Errcode: 28)]
SELECT t.*, tt.* FROM wp_terms AS t INNER JOIN wp_term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy IN ('product_tag') AND tt.count > 0 ORDER BY tt.count DESC LIMIT 45

or:

SELECT t.*, tt.* FROM wp_terms AS t INNER JOIN wp_term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy IN ('product_tag') ORDER BY t.name ASC LIMIT 200

Unfortunately, I do not know what happened, I mean, when this started.

I’ve done almost everything…

I’ve activated other theme, deactivated all plugins, reinstalled WordPress, rebooted mysql and nothing works.

As you can see in the image below I have many tags, but none is shown as they should:

https://i.stack.imgur.com/hedpv.jpg

My WordPress is up to date (4.4.1) either my plugins.
I’ve verified my database to make sure that the tags are still there, and they are.

Can someone help?

Thanks.