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 xsane 's PO files:

gettext: backend-po/newbackend.po: can't guess language
gettext: backend-po/umax.de.po:380: duplicate message definition...
backend-po/umax.de.po:373: ...this is the location of the first definition
backend-po/umax.de.po:396: duplicate message definition...
backend-po/umax.de.po:377: ...this is the location of the first definition
backend-po/umax.de.po:472: duplicate message definition...
backend-po/umax.de.po:449: ...this is the location of the first definition
msgfmt: found 3 fatal errors
gettext: backend-po/umax.ja.po:285:81: syntax error
backend-po/umax.ja.po:380: duplicate message definition...
backend-po/umax.ja.po:373: ...this is the location of the first definition
backend-po/umax.ja.po:396: duplicate message definition...
backend-po/umax.ja.po:377: ...this is the location of the first definition
backend-po/umax.ja.po:472: duplicate message definition...
backend-po/umax.ja.po:449: ...this is the location of the first definition
backend-po/umax.ja.po:512: missing 'msgstr' section
backend-po/umax.ja.po:523: missing 'msgstr' section
msgfmt: found 6 fatal errors
gettext: backend-po/umax.po: can't guess language
gettext: backend-po/umax1220u.sr.po:385: duplicate message definition...
backend-po/umax1220u.sr.po:378: ...this is the location of the first definition
backend-po/umax1220u.sr.po:401: duplicate message definition...
backend-po/umax1220u.sr.po:382: ...this is the location of the first definition
backend-po/umax1220u.sr.po:477: duplicate message definition...
backend-po/umax1220u.sr.po:454: ...this is the location of the first definition
msgfmt: found 3 fatal errors
      

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.