Registration, Buddypress, and Invite Codes

Hi. I've asked this question before, but let me rephrase it.

My Membership site has one New Member membership level. I am using Buddypress too.
I have activated the Invitation Codes Addon (to stop spammers), and the Buddypress Integration Addon. However, the Buddypress Addon means no Invitation Code is required to Register.

Conversely, with the normal Membership2 Registration, the registration process goes in a circle, and never gets to the Registration Complete page.

Can I ask for some direct help on this please, as it's driving me nuts?

I have reactivated Support access, and the site was previously accessed by Vaughan and Michael Bisset.

Thank you for your help.