I have a client who is very keen to use the AB testing facility in CiviMail. they are currently running on CiviCRM 4.7.27 and shortly to update. When they set up an AB mailing, they are specifying that 10% of the group should be sent version 'A', 10% should be sent version 'B', and then the remainder get sent the final choice, which that should be. In practice they are seeing that the entire group is sent version 'A', no-one gets sent version 'B' (and so there is no point in sending the final mail). I've checked through their workflow and it looks to me that they are doing everything by the book. I can't find any logged issues about this (maybe no-one is using it?). Are we doing something wrong, or is this functionality just broken?
Any pointers most welcome.