Initially reported via forums
https://forum.vyos.io/t/rpki-migration-failure/6592
Upgrade from 1.2.6-S1 using the following config will trigger this error:
set protocols rpki cache rtr.rpki.cloudflare.com address 'rtr.rpki.cloudflare.com' set protocols rpki cache rtr.rpki.cloudflare.com port '8282'