Last summer my host moved their datacenter from florida to texas. A lot of servers.  When each server was moved the permissions had to be reset on any of my customers websites on that server.  Occasionally one was missed and they received errors until they notified me.

Over the years Amazon has made huge changes how their data is accessed.  Occasionally that has caused problems with a few websites.

In general any critical issues with the websites are addressed quickly once I am notified.

Andy