The sysctl kern.ngroups cannot be changed, even setting it in /boot/loader.conf has no effect. The 16 groups limit is a bit low for an unchangeable magic number.
How-To-Repeat: # echo kern.ngroups=\"32\" >> /boot/loader.conf
# shutdown -r now
# sysctl kern.ngroups
Please refer to :
That means it's difficult to fix. Not that it shouldn't be fixed.