I'd like to propose a new classification for bugs in Bugzilla -- to allow easier grouping of PRs about ports which, though they build/install fine from scratch, fail if a version (earlier or otherwise) of the same port is already found on the build-system. I'm not sure, how to best name it -- "upgrade-failure" or "port-upgrade-failure"?
Thanks for your suggestion Mikhail. We're working on growing the set of keywords available to make discovery, classification and filtering of issues much easier.
^Triage: reassign.