[2.1.0] Ubooquity doesn't start on Synology

I followed this tutorial https://vaemendis.github.io/ubooquity-doc/pages/tutorials/install-on-synology.html to install Ubooquity on my Synology DS916+ (DSM 6.1.3-15152 Update 1) with Java 8 (1.8.0_141).

However when I issue the start ubooquity command the service starts and stops almost immediately. I can't figure out what's happening, and I'm stuck on how to proceed troubleshooting.

This is my ubooquity.conf file:

start on started httpd-user

stop on runlevel [06]

exec /var/packages/Java8/target/j2sdk-image/bin/java -jar -Xmx1024m /var/packages/Ubooquity/Ubooquity.jar -port 2202 -webadmin -headless -workdir "/volume1/Comix/Ubooquity"

I have tried to change the workdir to /volume1/Comix and also leave it out completely, but to no avail.

Since there's no ubooquity folder in my workdir (/volume1/Comix/) yet there's no logfile to look at.

Is there another log I can take a look at to push me in the right direction?

Or is there someone here who can help me out?