You can check if a PO file is valid with the following command:

        msgfmt -c -o /dev/null <po file>
      

The following errors were found in vim 's PO files:

gettext: src/po/ja.sjis.po:486:33: invalid control sequence
src/po/ja.sjis.po:535:18: invalid control sequence
src/po/ja.sjis.po:686:13: invalid control sequence
src/po/ja.sjis.po:819:16: invalid control sequence
src/po/ja.sjis.po:867:24: invalid control sequence
src/po/ja.sjis.po:1010:30: invalid control sequence
src/po/ja.sjis.po:1066:28: invalid control sequence
src/po/ja.sjis.po:1075:18: invalid control sequence
src/po/ja.sjis.po:1299:15: invalid control sequence
src/po/ja.sjis.po:1425:26: invalid control sequence
src/po/ja.sjis.po:1428:29: invalid control sequence
src/po/ja.sjis.po:1660:32: invalid control sequence
src/po/ja.sjis.po:1684:68: invalid control sequence
src/po/ja.sjis.po:1687:49: invalid control sequence
src/po/ja.sjis.po:1702:52: invalid control sequence
src/po/ja.sjis.po:1705:41: invalid control sequence
src/po/ja.sjis.po:1741:36: invalid control sequence
src/po/ja.sjis.po:1769:37: invalid control sequence
src/po/ja.sjis.po:1949:33: invalid control sequence
src/po/ja.sjis.po:2382:16: invalid control sequence
msgfmt: too many errors, aborting
      

Please ask the translator (identified by the Last-Translator field in the PO file), the language team (identified by the Language-Team field) or debian-i18n for a fix.