Disable features in beta versions
Releasing beta versions of a software, pointing to production servers is a reality (it has been happening for a while). But you have to be a bit wiser about it.
If the purpose of a beta version is to test performance of certain features, disable the features that could bring problems when pointing at production servers (that you do not need tested).
If this is not possible, inform the beta testers what you need them to test, and what not to test. Also, you should have a dedicated project online to keep track of different devices, bugs and known issues that these testers can check (to see if they are reporting something that is already reported, or to know what to avoid).
I understand why you had to perma-ban testers, but the way the beta was handled wasn't professional. For what I read, any in-game purchase came with a message saying that these would be undone by the end of the testing. If this wasn't the case (or you found an exploit after that, through gifting), you should have let users know this was an exploit and do not make purchases with that version of the game.
I also understand the situation was very complex and required a larger pool of testers. But, after what happened, I wouldn't expect users to help you beta-test anything. And neither should you. You need to invest more in testing, the last month has brought that into light a lot. Please do.