I found a bug on openntpd-6.2p3-4, the bug is fixed with openntpd-6.2p3-5 version but need a manual intervention :
first update the package then
if the ntpd daemon is running, first stop it :
# s6opts disable ntpd
then remove the ntp user
# userdel ntp
recreate it by applysys prog
# applysys openntpd.conf
finaly enable the daemon
# s6opts enable ntpd