I take that back. Replication is working on 4/6 servers.
If I add a user on any of those 4 it shows up on the other 3. The 2 outliers don't
seem to pick up the new user. If I check the 2 outliers I get this
Error (18) Replication error acquiring replica: Incremental update transient error.
Backing off, will retry update later. (transient error)
Which seems to be saying that it's just delayed, which can sometimes happen in an MMR
setup. I will recheck these 2 later to see if they eventually pick up the new test user
I've created and that is present on 4 of them.