[German]On 4.10.2021, there was a six-hour service outage at Facebook at around 17:30, which also included the Instagram and WhatsApp services. I had reported in the post Facebook, Instagram and WhatsApp worldwide down. Now Facebook has provided a more comprehensive explanation of the reasons for the outage. Details may be read within the article More details about the October 4 outage from Facebook.
I wouldn't believe a word Facebook says.
If they say it was "A" it was probably "B".