Group Replication doesn't like "::ffff:10.12.1.2" as an IP Address

[IGG t]

I'm trying to set up group replication using 3 x MySQL 8.0.16 databases on 3 x Debian 9.9 (stretch) servers, but when I start up the second Node it fails. The error log reports:

[GCS] Connection attempt from IP address ::ffff:10.12.1.2 refused. Address is not in the IP whitelist.
But if I add a whitelist:

group_replication_ip_whitelist="::ffff:10.12.1.2";
I get:

[GCS] Invalid IP or subnet mask in the whitelist: "::ffff:10.12.1.2";
Is this an issue with the server at my end, or an issue with Group Replication not understanding the IP Address?

My configuration is:

server_id=<different for each one>
gtid_mode=ON
enforce_gtid_consistency=ON
binlog_checksum=NONE
transaction_write_set_extraction=XXHASH64
group_replication_group_name="8112d18e-9e6e-11e9-a526-0e51be33883f"
group_replication_start_on_boot=off
group_replication_local_address= "10.12.1.1:33061" /*This is different for each one*/
group_replication_group_seeds= "10.12.1.1:33061,10.12.1.2:33061,10.12.1.3:33061"
group_replication_bootstrap_group=off
If I look on the first nodes error log I can see:

Connection attempt from IP address ::ffff:10.12.1.2 refused. Address is not in the IP whitelist.'
But again, adding it to a whitelist throws the above error about there being an invalid IP Address,