I have found a bug with xquartz 2.7.11
It seems that installing xquartz on 10.12 and gnubg runs fine.
Also, installing xquartz on 10.11, gnubg will also run fine.
The bug that I found is this.
1. install xquartz 2.7.11 on OSX 10.11
2. then upgrade OSX to 10.12
3. gnubg no longer works.
I might get through one whole game, but the game will freeze and there is no other option but to quit out of X11 and restart.
I tried deleting gnubg and reinstalling quarts 2.7.11 but this did not work.
Do you have a fix coming for this?
I am running this on an iMac that is Late 2009, but my dad also has the same problem on a machine he bought 2 years ago.
Is there a way to uninstall xquartz so I can reinstall it? that might be a temporary fix.
You can see https://www.xquartz.org/FAQs.html, but you shouldn't need to uninstall first.
Please do make sure you re-install after major OS upgrades because the OS upgrade removes the /usr/X11 and /usr/X11R6 symlinks.