Similar issue here, would be good to know what resolved this? Thx,.
PMG is behind NAT -> public proxmox host IP vmbr0 with MTU 1500, and private PMG IP vmbr1 with MTU 1450.
Seems to be expected: https://pve.proxmox.com/pve-docs/chapter-pvesdn.html#pvesdn_setup_example_vxlan
VXLAN zone...