Custom redirect URL on confirmation with API subscription

Custom redirect URL on confirmation with API subscription

If a user is added via the ListSubscribe API call and then clicks through the confirmation email they receive, they are redirected to a generic thank you page even if a custom URL thank you page is defined for the list's default mailing list.  This didn't use to behave this way.  In fact, one of our 5 lists still works properly and uses the custom redirect URL while the rest all use the generic Zoho page when subscribing through the API.  Has anyone else had this problem?  Any idea how to fix it?