Today I learned that the VRRP documentation for Mikrotik routerOS is somehow misleading. For the examples used for IPv4 and IPv6 VRRP they use the same VRRP interface name, but this doesn’t work if you configure both IPv4 and IPv6 addresses to the same interface. You need to add separate interfaces, for example, downlink-vrrp-v4 and downlink-vrrp-v6, with separate router IDs and with the correct v3 protocol to get it working. Also, they show the non-active IP addresses as invalid if you print the IPs; this is normal but looks like a problem with duplicate address detection.
Here is a working example from a config export:
/interface vrrp
add interface=downlink-bond name=downlink-vrrp-v4 priority=100
add interface=downlink-bond name=downlink-vrrp-v6 priority=100 v3-protocol=ipv6 vrid=2