18 months ago my company decided to run an ad campaign on various platforms: FB, Twitter, Google search and direct buys of banner ads.
On all platforms, the campaign was targeted to most EU countries + Switzerland. For business reasons we were not interested in promoting this outside these countries.
On Facebook, out of all options, we decided to promote a post, targeted to EU countries, this post included a custom bitly link to our campaign's website, etc. A few hours after launching the campaign, we checked on the post: likes/engagement, CTR, bitly link, etc. We were shock to see that almost 90% of all likes to the post and clicks where made from Brazil. Facebook had been promoting our post in Brazil and not (marginally) in the countries we specified – I clicked on a long list of Facebook profiles who had liked our promoted post and these were primarily from the Sao Paulo region. I double checked bitly's stats with the our analytics to check who landed on our site via the campaign link. Again, c. 90% from Brazil.
The first thing after that finding was to check that the campaign was correctly setup, and it was. We immediately stopped the campaign and reached out to FB via a form (they have no email nor telephone) telling them about the issue, we included screenshots and other relevant information. We never heard from Facebook. We spent around €2,000 on a useless campaign targeted to an audience which wasn't our target market. We have never used FB again.