wanderlustig
If you set a waypoint on the slip lane, it worked fine. So I think the problem was not in the slip lane itself, but in the intersection with Patterson Road to the north. Southbound routing got sent via Cummins Road instead. This may have been because the Nepean-Cummins slip lane was missing a traffic light and the routing engine thought it was more efficient. I've fixed up that intersection in changeset #54014479. Let's see how it works once the new map propagates in 2.5 weeks.