We are running 2.9.0.beta8
The update it asks us to do is docker_manager 45986ad4 (Comparing 45986ad40ec642ea617a083aecc75e0078878fb7...90a8a6c6cae0bba01de7fdf340da1ab878bff913 · discourse/docker_manager · GitHub)
It is a standard install from docker, however we run a couple plugins (but nothing unusual, really. No custom code so far)
At this point (without error log) I cannot really tell more, I guesss we’ve to bite the apple again and after a backup, run the update and if it fails again, submit the logs…