When configuring rpki with a hostname, any dashes in the FQDN are replaced with underscores when the config is applied.
set protocols rpki cache rtr-ham1.mhl-lab.net port '3323' set protocols rpki cache rtr-ham1.mhl-lab.net preference '2'
becomes
rpki rpki polling_period 300 rpki cache rtr_ham1.mhl_lab.net 3323 preference 2 exit