A couple months ago, I started getting I/O errors (see below) whenever I tried to do journalctl
You are able to read all the journald files, aren't you? You are running cp -r so it looks like so. `cp` would die with non-zero exit status if there were read errors I guess. If it's possible to read the file, journalctl should not segfault IMO, so it should be OK to file an issue.
-- Kind regards, Damian Nowak StratusHost www.AtlasHost.eu