improper rollback on upgrade failure
Behaviour probably not strictly related to version, but for context. (I accept that those old versions are no longer supported.)
Migrating a 2.1.0 instance to 2.2.8 hit an error relating to a package rename (pkg_resources.DistributionNotFound: rhodecodemomentum) and attempted rollback.
instancename/profile symlink was rolled back, but not the rhodecode.ini file, resulting in the app egg still pointing to egg:rhodecodemomentum and the instance failing to restart.
Manually renaming rhodecode.backup_2.1.0.ini back fixed the issue.