(Was "shutting down nfs from either GUI fails when done a second time")
This appears to occur independently of the nfs service configuration and the presence or absence of valid shares. /etc/rc.d/nfsd restart and forcestop work from the command line, even after changing to /bin/sh. When the service is stopped from the GUI (new or old) first time after a reboot it stops and can be restarted normally. When the 'stop' action is repeated from the GUI the nfsd process is not stopped and becomes unkillable with "kill -9". Rebooting is the only option I have found to restart the NFS service.
Workaround: restart nfsd from the command line after a change of configuration.
This ticket is to continue investigating the root cause.