Group Replication On Windows wont start. Error 3092

[IGG t]

I have installed 3 fresh instances of MySQL 5.7.17 on my local PC, I have done nothing beyond initializing and logging in to them (changing the root password). I use the same password and process on all three databases.

I then followed the instructions in http://dev.mysql.com/doc/refman/5.7/en/group-replication.html to set up Group replication.
e.g. in the my.ini file I added:
[mysqld]
datadir=c:/mysql/1/data/
basedir=c:/mysql/1/
port=3306

# Replication configuration parameters
server_id=1
gtid_mode=ON
enforce_gtid_consistency=ON
master_info_repository=TABLE
relay_log_info_repository=TABLE
binlog_checksum=NONE
log_slave_updates=ON
log_bin=binlog
binlog_format=ROW

# Group Replication configuration
transaction_write_set_extraction=XXHASH64
loose-group_replication_group_name="aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"
loose-group_replication_start_on_boot=off
loose-group_replication_local_address= "127.0.0.1:33061"
loose-group_replication_group_seeds= "127.0.0.1:33061,127.0.0.1:33062,127.0.0.1:33063"
loose-group_replication_bootstrap_group= off

I then start group replication as follows:

SET SQL_LOG_BIN=0;
CREATE USER rpl_user@'%';
GRANT REPLICATION SLAVE ON *.* TO rpl_user@'%' IDENTIFIED BY 'rpl_pass';
FLUSH PRIVILEGES;
SET SQL_LOG_BIN=1;

CHANGE MASTER TO MASTER_USER='rpl_user', MASTER_PASSWORD='rpl_pass' FOR CHANNEL 'group_replication_recovery';

SET GLOBAL group_replication_bootstrap_group=ON;
START GROUP_REPLICATION;
SET GLOBAL group_replication_bootstrap_group=OFF;

SELECT * FROM performance_schema.replication_group_members;

CREATE DATABASE test;
use test;
CREATE TABLE t1 (c1 INT PRIMARY KEY, c2 TEXT NOT NULL);
INSERT INTO t1 VALUES (1, 'Luis');
SELECT * FROM t1;

So far so good. I then repeat the process on database 2. (changing the paths `c:/mysql/2/`, `server_id=2`, and the ports to `3307` and `33062`).

I then restart the database, and run through the process to start group replication (exactly the same as above, but without setting the `group_replication_bootstrap_group=ON`).

But, instead of starting, I get an error:

Error Code: 3092. The server is not configured properly to be an active member of the group. Please see more details on error log.

Looking in the error log it says:

[ERROR] Plugin group_replication reported: 'This member has more executed transactions than those present in the group. Local transactions: 920e25d9-0d5f-11e7-8b3f-c85b768dc0db:1 > Group transactions: 7f04cd86-0d5f-11e7-963c-c85b768dc0db:1,
aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:1-4'

If I subsequently set `group_replication_allow_local_disjoint_gtids_join option=true` then it starts ok. But that seems to defeat the point.

Am I missing something here? Have I misunderstood, or is this potentially a BUG, or a documentation error?

I tried again on database 3, and got the same error.