I've found some issues today where deleting immediate memberships does not always do the right thing in terms of deleting effective memberships. I'll add more details of the issues when I have a chance to further dive into the problems.

I've assigned this issue to the 1.4.0 release rather than the 1.3.1 release since it doesn't seem like a critical issue at the moment (nobody else has reported the problem yet). But if this needs to be resolved in 1.3.1 we can certainly aim for that.