Arrrrr! Thanks for your suggestion, but i figured it out. The TFTP service was only binding to the IPv4 address. I’m dual stacked on the gitlab / tftp server and have A and AAAA records for it in DNS. VyOS was preferring the IPv6 connection when using FQDN.
Once i set the flag to IPv6, the service bound to both v4 and v6. Everything worked.
Thanks!