[Observium] changes to $config['frontpage']['custom_traffic']['ids'] ignored

We replaced our edge routers over the weekend and I updated the list of port id's in $config['frontpage']['custom_traffic']['ids'] with the new ones from the new routers; however, the custom graph on the front page hasn't changed and still lists the old interfaces (on the now shut-down routers).

What else do I need to do?

Thanks.