Dynamic collapse cards, Accordions

Has anyone found the correct definitive way of populating these new card collapse elements, when inside a repeat region. I can not get the parent and its relative child to have the same ID.

Either I have them all open when any are clicked or I cant get them to open at all when attempting to add a $index from the repeat to make them unique IDs.
It almost seems as though the dmx-bind:id attribute only works on displayed elements.