RabbitMQ 3.12.13 head_message_timestamp is null

Question

I am using the RabbitMQ API in version 3.12.13 to retrieve the head message timestamp for all queues, but the API is returning null for most (but not all) queues.

We have the value set in our rabbitmq.conf file:

message_interceptors.incoming.set_header_timestamp.overwrite = true

and I am calling the API at {rabbitmqURL}:{port}/api/queues

Has anyone else had this issue?

Thanks