Current width of "Other languages" box is wider by 1 pixel than required.
See screenshot from meta:Meta:Administrators :
This style is defined in the ext.translate.tag.languages.css.
In my opinion, this is because defining borders twice - firstly in the "mw-pt-languages" and secondary in the "mw-pt-languages-label".
This may be fixed through addition
box-sizing: border-box;
into 'mw-pt-languages':
(the rest of the view does not change)