I'm running 5.20 on a RB1000, and one specific VLAN interface will not respond to any IPv6 addresses attached to it.

Here are some VLANs from the RB1000:
add arp=enabled disabled=no interface=ether3 l2mtu=1596 mtu=1500 name="260 - avairis" use-service-tag=no vlan-id=260
add arp=enabled disabled=no interface=ether3 l2mtu=1596 mtu=1500 name="254 - solusvm VMs" use-service-tag=no vlan-id=254
add arp=enabled disabled=no interface=ether3 l2mtu=1596 mtu=1500 name="255 - solusvm mgmt" use-service-tag=no vlan-id=255



If I attach an IPv6 address to 260 or 255, I can ping it.
If I attach an IPv6 address to 254, pings timeout.

Have tried with several different IPv6 addresses, and it's 100% reproducible.

Any thoughts on what could keep an IPv6 address from working on an interface?

Thanks!