Translation of CoursePress disappearing ???

Greetings,

Something weird happen... I translated the Coursepress plugin in French, and following your instructions, added this plugin in "mywebsite.com/wp-content/plugins/coursepress/languages"... It was working, so I'm sure I didn't do any mistake.

Then, a few weeks later, we discovered that this translation stopped displaying, and the .mo et .po french files of the translation also disappeared in the "languages" folder.

I added those files back and the translation is displaying again, but it's weird. I didn't do anything to the website except the regular update. Would it be possible that an update removed these translation files ?

Technically, the translation system with .po and .mo files on the "languages" folder should be update proof, isn'it ?

Any idea of what could have gone wrong, so we can make sure it doesn't happen in the future ?

Thanks a lot.