It seems like the dropdown reasons for blocking (ipbreason-dropdown) now behaves similar to the problem described in bug 48956:
When the user has an interface language different from that one of the wiki, the dropdown reasons are loaded from the i18n file for that language, not, as it was before, from the local customization (which is obviously always in the language of the wiki).
It only appears on non-Wikipedia, so I guess it's related to the rollout of 1.23wmf15.
Version: 1.23.0
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=61987
https://bugzilla.wikimedia.org/show_bug.cgi?id=62131