I'm not sure what the circumstances are, but it looks like unpaper can attempt to write a temporary file that already exists [0]. This then fails the consumption. As per daedadu's comment simply letting unpaper overwrite files fixes this. [0] unpaper: error: output file '/tmp/paperless/paperless-pjkrcr4l/convert-0000.unpaper.pnm' already present. See https://web.archive.org/web/20181008081515/https://github.com/danielquinn/paperless/issues/406#issue-360651630