I downloaded the Platform independent binary: http://sourceforge.net/projects/geoserver/files/GeoServer/2.13-beta/geoserver-2.13-beta-bin.zip
and added the WPS plugin and the WPS-Download community plugin: https://build.geoserver.org/geoserver/2.13.x/community-latest/geoserver-2.13-SNAPSHOT-wps-download-plugin.zip
I then followed the instructions in the documentation to download the raw nurc:Img_Sample layer via WPS gsownload
The process fails with this message:
The stack trace is the following:
If I create a new store and a new layer from the same file (all default options) the process completes without errors.
I guess it is a backward compatibility issue, looking at the coverage.xml files differences, I noticed the new one has additional info in the "coverage -> dimensions -> coverageDimension" tags
Java version "1.8.0_161"