Summary
When a URL is changed/deleted on the catalog, the rewriter does not receive this change. Since the rewriter is not notified about it, the URL is still pointing to the wrong type, which can also lead to problems on the IS.
This can also happen when creating new category/subcategory routes on the catalog. The rewriter sometimes will need you to run the bootstrap query to receive those routes.
Simulation
Try deleting an existing brand from the catalog Run the mutation to see how this path is being received on the rewriter
{internal{ get(path:"/brand"){ from declarer query disableSitemapEntry }}}
If you look for that brand on the storefront, it will still be pointing to a map=b
You can also check how this path is being returned on the pageType; if it is a fullText, the pageType was updated, and the rewriter didn't.
Workaround
Try deleting the route manually from the rewriter:
mutation{ internal{ delete(path:"/path"){ from id resolveAs } }}
Try running the bootstrap query to update the rewriter:
{bootstrap { brands categories}}