Its always good practise to add the active DNS servers to the Juniper device. This can be found under \Device setup\Addresses\DNS servers. (One per line)
To view the current DNS settings (Command line)
show -run dns
When you have added your DNS server the Juniper will resolved the DNS names after the next polling interval. It will then display the correct name for the IP address.
I have seen this many times and it usually happens when a site has been offline for a few days or you add a new site. When I bring the site online and the polling interval pass my DNS names will be pulled in.