We recently converted our documentation to use the deck of cards for easier navigation, but unfortunately this broke our table of contents on the same page.

There are a couple of workarounds (see comment), but they are very messy and not sustainable over the lifespan of the page. If someone creates a new page, for instance, the workaround ToC does not update.

Repro:
1) Open a page with a working ToC
2) Add the Deck of Cards macro
3) Add Cards for the number of headings you need
4) Put top-level headings into each Card under Deck of Cards
5) Save. Note that the ToC now only works if selecting items from the currently open card.