I've just tried your nightly (from Dec 8). I was able to upgrade the package once. /etc/sudoers.d/ folder was empty bug #675 was corrected.
Removing the package manually gave me:
warning: file /etc/sudoers.d/x2goserver: remove failed: No such file or directory
It seems that file was never there after the upgrade. While trying to re-install the package, I get a new error in the PREIN scriplet. I'll make some more tests and if the problem persist, open a separate bug.
I will make a test environment and try to build your package from source and I will be able to troubleshoot this issue a bit more.
Thanks for the follow-ups.