We wanted to inform you that we just ran into this issue for the first time and “launcher rebuild app” didn’t help, so we followed the advice from @eviltrout by flushing Redis:
Hitting the “Reset Upgrade” button sounded too risky for us as it suggests anything would be rolled back, which we didn’t want to do because everything seemed to work flawlessly after the upgrade got applied successfully, as always.
At this place, we want to tell you that every time we hit the “Upgrade Discourse” button, we are again amazed by the shipping and production deployment quality of Discourse. Kudos to the whole team and keep up the spirit!