Major Description
The current unsubscribe processing is identifying a 'null-source lookup' attach as indication to immediately unsubscribe a durable subscription, performing some trickery with capabilities. There are actually many other reasons reasons a client might do this type of attach, which might lead to prematurely ending a subscription. Fully closing (rather than a non-closing detach) the durable subscription link is to be the signal ending the subscription. The related code should be fixed to resolve this, and generally cleaned up to simplify things.