I can verify that this also occurs on my compute servers running Ubuntu 14.04LTS and 16.04LTS.
Commenting the line:

in x2goagent.options does resolve the issue, *but* there is a comment above that line:
# Disable BIG-REQUESTS, nx-libs does not implement this extension correctly.
# Leads to all sorts of weird crashes if left enabled.
which unfortunately has proven to be true for my instances. The performance and reliability of x2go has dropped substantially since commenting the line. 
Can we please raise the priority of this bug to restore performance? 
Regards, Adrian.