3.7.4 ignoring translated error phrases
 

I'm trying to modify the "moderateuser" phrase (which is an error phrase), but vBulletin is not honoring my translation. I have tried clearing local cache, downloading/uploading language files, editing the standard phrase on the server (in install/vbulletin-language.xml), disabling/re-enabling memcached, and disabling/re-enabling hooks. The correct phrase now appears as standard, but vBulletin is not using it. What gives?

Other phrase translations are working correctly.

Where else should I look? Please advise.