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 clementine 's PO files:

gettext: src/translations/af.po:1559: duplicate message definition...
src/translations/af.po:1556: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/ar.po:1563: duplicate message definition...
src/translations/ar.po:1560: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/be.po:1558: duplicate message definition...
src/translations/be.po:1555: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/bg.po:1562: duplicate message definition...
src/translations/bg.po:1559: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/bn.po:1556: duplicate message definition...
src/translations/bn.po:1553: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/br.po:1561: duplicate message definition...
src/translations/br.po:1558: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/bs.po:1555: duplicate message definition...
src/translations/bs.po:1552: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/ca.po:1563: duplicate message definition...
src/translations/ca.po:1560: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/cs.po:1568: duplicate message definition...
src/translations/cs.po:1565: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/cy.po:1554: duplicate message definition...
src/translations/cy.po:1551: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/da.po:1572: duplicate message definition...
src/translations/da.po:1569: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/de.po:1613: duplicate message definition...
src/translations/de.po:1610: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/el.po:1573: duplicate message definition...
src/translations/el.po:1570: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/en_CA.po:1556: duplicate message definition...
src/translations/en_CA.po:1553: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/en_GB.po:1557: duplicate message definition...
src/translations/en_GB.po:1554: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/eo.po:1558: duplicate message definition...
src/translations/eo.po:1555: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/es.po:1590: duplicate message definition...
src/translations/es.po:1587: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/et.po:1559: duplicate message definition...
src/translations/et.po:1556: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/eu.po:1558: duplicate message definition...
src/translations/eu.po:1555: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/fa.po:1560: duplicate message definition...
src/translations/fa.po:1557: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/fi.po:1560: duplicate message definition...
src/translations/fi.po:1557: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/fr.po:1601: duplicate message definition...
src/translations/fr.po:1598: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/ga.po:1555: duplicate message definition...
src/translations/ga.po:1552: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/gl.po:1559: duplicate message definition...
src/translations/gl.po:1556: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/he.po:1561: duplicate message definition...
src/translations/he.po:1558: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/he_IL.po:1553: duplicate message definition...
src/translations/he_IL.po:1550: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/hi.po:1556: duplicate message definition...
src/translations/hi.po:1553: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/hr.po:1559: duplicate message definition...
src/translations/hr.po:1556: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/hu.po:1565: duplicate message definition...
src/translations/hu.po:1562: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/hy.po:1554: duplicate message definition...
src/translations/hy.po:1551: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/ia.po:1556: duplicate message definition...
src/translations/ia.po:1553: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/id.po:1575: duplicate message definition...
src/translations/id.po:1572: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/is.po:1560: duplicate message definition...
src/translations/is.po:1557: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/it.po:1559: duplicate message definition...
src/translations/it.po:1556: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/ja.po:1568: duplicate message definition...
src/translations/ja.po:1565: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/ka.po:1556: duplicate message definition...
src/translations/ka.po:1553: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/kk.po:1554: duplicate message definition...
src/translations/kk.po:1551: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/ko.po:1570: duplicate message definition...
src/translations/ko.po:1567: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/lt.po:1559: duplicate message definition...
src/translations/lt.po:1556: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/lv.po:1559: duplicate message definition...
src/translations/lv.po:1556: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/mk_MK.po:1557: duplicate message definition...
src/translations/mk_MK.po:1554: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/mr.po:1554: duplicate message definition...
src/translations/mr.po:1551: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/ms.po:1557: duplicate message definition...
src/translations/ms.po:1554: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/my.po:1554: duplicate message definition...
src/translations/my.po:1551: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/nb.po:1559: duplicate message definition...
src/translations/nb.po:1556: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/nl.po:1565: duplicate message definition...
src/translations/nl.po:1562: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/oc.po:1554: duplicate message definition...
src/translations/oc.po:1551: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/pa.po:1554: duplicate message definition...
src/translations/pa.po:1551: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/pl.po:1574: duplicate message definition...
src/translations/pl.po:1571: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/pt.po:1562: duplicate message definition...
src/translations/pt.po:1559: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/pt_BR.po:1566: duplicate message definition...
src/translations/pt_BR.po:1563: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/ro.po:1568: duplicate message definition...
src/translations/ro.po:1565: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/ru.po:1583: duplicate message definition...
src/translations/ru.po:1580: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/si_LK.po:1553: duplicate message definition...
src/translations/si_LK.po:1550: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/sk.po:1560: duplicate message definition...
src/translations/sk.po:1557: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/sl.po:1560: duplicate message definition...
src/translations/sl.po:1557: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/sr.po:1559: duplicate message definition...
src/translations/sr.po:1556: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/sr@latin.po:1558: duplicate message definition...
src/translations/sr@latin.po:1555: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/sv.po:1578: duplicate message definition...
src/translations/sv.po:1575: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/te.po:1554: duplicate message definition...
src/translations/te.po:1551: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/tr.po:1573: duplicate message definition...
src/translations/tr.po:1570: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/tr_TR.po:1590: duplicate message definition...
src/translations/tr_TR.po:1587: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/uk.po:1556: duplicate message definition...
src/translations/uk.po:1553: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/uz.po:1555: duplicate message definition...
src/translations/uz.po:1552: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/vi.po:1560: duplicate message definition...
src/translations/vi.po:1557: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/zh_CN.po:1569: duplicate message definition...
src/translations/zh_CN.po:1566: ...this is the location of the first definition
msgfmt: found 1 fatal error
gettext: src/translations/zh_TW.po:1557: duplicate message definition...
src/translations/zh_TW.po:1554: ...this is the location of the first definition
msgfmt: found 1 fatal error
      

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.