Links on repro map are built using Point Links instead of Smart Links and crowd manager recognize them correctly (LinkId = 0, not a smart link).
StartUsingCustomLink() never gets called in the CrowdManager when an AI with a UCrowdFollowingComponent begins to traverse a NavLinkProxy that has been placed in the world.
The link UserID always returns 0, so it believes that we never traverse a valid Custom link.
Head over to the existing Questions & Answers thread and let us know what's up.