Rails console goes funky after several commands since Rails upgrade

Since RC1 was deployed to GitLab.com the Rails console has consistently gone wonky after 1-2 queries. @yorickpeterse @balameb and I have all seen it. Is this a Rails bug (searched, but didn't find much) or something else?

Unsure if related, but certain things also cause a segfault in the console. @yorickpeterse saw this and so did I today.