The message key "user-fanbox-title" is used twice: in SocialProfile and FanBoxes: https://codesearch.wmcloud.org/search/?q=user-fanbox-title&i=nope&files=en&excludeFiles=&repos=
Therefore translatewiki has a duplicate key.
I tried to replace one of the keys with a unique one but I could not find any usage of the message key in the program code itself. Maybe both are unused?