Problem with getting cturra/ntp to run under docker

Starting to learn docker. Got Pihole up and running but not having any luck with curra/ntp.

According to the page, all I should have to do is

# pull from docker hub
$> docker pull cturra/ntp

# run ntp
$> docker run --name=ntp             \
              --restart=always       \
              --detach=true          \
              --publish=123:123/udp  \
              --cap-add=SYS_NICE     \
              --cap-add=SYS_RESOURCE \
              --cap-add=SYS_TIME     \

I can see it try to come up but wont stay running.
Would appreciate any suggestions on what to look at or if there is another ntp container from that I should try.