Whenever, I right click on my service model and choose “Update Service Stack Reference”. The BaseURL at the top of my ServiceModel.dtos.cs gets set back to https://www.domain.com
You should be able to set the AppHost PathBase to a prefix for the API as required. Optionally, it will detect the use of ASPNETCORE_APPL_PATH if that is set.
Can you try /sub/api/metadata path links, are they also not working?