Seagate has a (quite recent) history of high failure rates on their hard drives. In fact there was a class action lawsuit on that point (that failed on a technicality).
My 3Tb external model just failed (in under 3 years), basically with the same symptoms. Yes, hard disks can fail, but not at these rates. I have 10yo+ drives still going strong.
I'll never, ever, ever buy a Seagate or Seagate-related product again. I hope everyone here sees this post.