Error 500: Internal Server error

ErrorMessage: Z3950ServerConnection: YAZ error: [1072] Query term includes characters that do not translate into the target character set; Server: 127.0.0.1:2332/default
#0 /srv/www/htdocs/europeana-local.at/mdm/classes/ErrorHandler/ExceptionErrorHandlerStrategy.php(40): ExceptionErrorHandlerStrategy->_echoMsg('ErrorMessage', -1, 'YAZ error: [107...', 'Z3950ServerConn...')
#1 /srv/www/htdocs/europeana-local.at/mdm/classes/ErrorHandler.php(224): ExceptionErrorHandlerStrategy->err('YAZ error: [107...', 'Z3950ServerConn...', -1)
#2 /srv/www/htdocs/europeana-local.at/mdm/classes/Z3950ServerConnection.php(651): ErrorHandler->err('YAZ error: [107...', 'Z3950ServerConn...')
#3 /srv/www/htdocs/europeana-local.at/mdm/classes/Z3950ServerConnection.php(243): Z3950ServerConnection->displayErrorIfOccured_()
#4 /srv/www/htdocs/europeana-local.at/mdm/classes/Z3950ServerConnection.php(703): Z3950ServerConnection->search(Object(SearchQuery), 'oai-DateStamp:d...', 1, 20)
#5 /srv/www/htdocs/europeana-local.at/mdm/feeds/index.php(61): Z3950ServerConnection->getRecords(Object(SearchQuery), 'oai-DateStamp:d...', 1, 20)
#6 {main}