hey Paolo,

I am really sorry for the delay of this reply as it is a public holiday for us here.

Sometime Facebook already cached your post data from their server, to fix this, you can copy your post URL and paste in Facebook debugger tool ( https://developers.facebook.com/tools/debug/og/object/ ) then click "Fetch new scrape information" button, it will clear all the cache and re-crawl your post data tag again.

it should work fine, you can take a look of my screenshot below.