Upgrade button is 500-ing for me

[DeanMarkTaylor (Dean Taylor)]

Problems like this are most commonly solved by rebuilding from the command line, see this post:

Manually update Discourse and Docker image to latest

This guide provides step-by-step instructions for manually updating Discourse, the Docker container, and the Ubuntu operating system on a self-hosted setup. Required user level: System Administrator SSH access to the server. If you self-host Discourse, you occasionally need to run a manual update via the command line to get the latest security releases and newest libraries. These updates are not picked up in admin/upgrade, which is why you’ll occa…