On the cy: wikipedia we have noticed that user "MediaWiki default" (a bot?) seems to run every 6 months or so and repeatedly resets many of the MediaWiki strings either to an older version which has been corrected or (even worse) to English. I've just had to edit :cy:MediaWiki:Go from "mynd" (travel) to "ewch" (imperative) again!
It is intensely annoying to have to repeatedly go through Special:Allmessages trying to find out what has been screwed up (our users usually notice when the labels of the editing tabs or the sidebar go crazy). I know you need to create new strings for new features in MediaWiki but for goodness' sake can the bot be altered so that it doesn't interfere with pre-existing strings?