All moderator message templates have lost their translations.
For instance, the translation for the template "question repetition" was made a long time ago and was available before the mod private message redesign.
This issue has been fixed. As I said in the comments, the tl;dr here is that we had an issue with line endings in the template strings (and any multi-line strings in general), which broke our translation lookups.
Sorry for the inconvenience and thanks for the report!