I tried editing Z1005 and Z18784 with the Russian user interface, and it looked like this:
I think that the problem is obvious from the screenshot, but if it isn't, I'm happy to add details.
It doesn't overflow on my laptop when I use Wikifunctions in English, but it happens consistently on all pages in Russian.
It also happens in Italian:
It probably has something to do with the length of the translation of the message wikilambda-about-widget-title. This message is short in English and German, so it doesn't happen there, but it's longer in Russian and Italian, so it breaks.
In Chechen (ce), it's two words, so something a bit weird happens: Before editing, the "About" label is shown in one line, but when editing, it becomes two lines. Screenshot:
