Erro 503 oai no método ListRecords OJS 3

OJS/SEER
#1

Quando executo o método ListRecords na revista http://unifatea.com.br/seer3/index.php/ECCOM/oai,

exibe o erro
Error 503 Backend fetch failed
Backend fetch failed

Guru Meditation:
XID: 11182218

Varnish cache server

Obs: disable_path_info = Off