Re-check your po file and see if the original word hasn’t a count beside it. Something like Members %s
. Many translation are omitting this or use an erroneous variable ( something like % or %d or…nothing). In any case, the translation should contain, if exist in the original, such variables.
Same remark if you use plugins or a theme who modify the menu.
You can also check for the new nav API examples you could eventually help you to rename the items, but only if nothing goes to work with translation itself.