After enabling versioned notifications, the queue versioned_notifications (info and error) keep filling up

We are using Openstack Rocky. Watcher needs versioned notifications to be enabled. However after enabling versioned notifications, the queues for versioned_notifications (info and error) keep filling up. How can we get around this issue? Based on the updates the the Watchers cluster data model, it appears that Watcher is consuming messages, but they still linger in these queues. What is the best way to resolve this?