We have been on OpenProject 12.5.8 and are attempting to upgrade to version 15.2. I am able to add the stable 15 package repository and perform the installation, but I get a 503 error and ruby processes run at 100%. I attempted to perform several point-level updates using URLs generated from packager.io but I get an error that I am running the latest version 12.5.8.

I also attempted to upgrade to the latest version of OpenProject 13 using the packager.io command below, but had the same results.

sudo wget -O /etc/apt/sources.list.d/openproject.list \  https://dl.packager.io/srv/opf/openproject/stable/13/installer/ubuntu/22.04.repo

Am I unable to upgrade due to the large gap between the versions? Should I attempt to perform a lower version installation (13 or 14) and restore data from my 12.5.8 server?