Clearly there is an underlying problem that needs to be ferreted out. There is very good tool which analyzes your i18n YAML as the Rails app, which I have found extremely helpful in debug.
Install and run this gem i18n-tasks: https://github.com/glebm/i18n-tasks.
To create a comprehensive report of the your i18n components:
$ i18n-tasks health
From their spec:
This gem analyses code statically for key usages, such as I18n.t('some.key'), in order to:
Report keys that are missing or unused.
Pre-fill missing keys, optionally from Google Translate.
Remove unused keys.
Thus addressing the two main problems of i18n gem design:
Missing keys only blow up at runtime.
Keys no longer in use may accumulate and introduce overhead, without you knowing it.
I'm not sure the gem was intended to be used as an i18n debug tool, but I have found it to be useful for debugging hard to find problems in i18n.