If the current forum language does not exist in the plugin, then overriding strings in the admin panel does not work.
As an example: if I have a plugin which only has english language translations, and somebody installs it on a french forum, the english strings will be used (this makes sense).
However, if the forum owner goes into the admin panel and tries to update the translation string, that change has no effect.
Ran into this issue again today with @Ogulcan. Is there any plan to get it fixed, and if not would someone be able to point me to the right area of the codebase so I can attempt to fix it myself?