It's quite common to bind to events on objects like models or collections etc. which will not be unbound just because the dom element is.
The problem is, you have a bunch of subviews which are registering events on some collection models... when you rerender your parent view your subviews get recreated but your previously created subviews stay in memory because the backbone events system still stores references to the old views which aren't really needed anymore. The only solution is to explicitly remove the events when subviews a destroyed (or better use a solution like in the submitted article) or use a library like https://github.com/marionettejs/backbone.eventbinder