Quorum queue temporary marked down during node restarts for any reasons such as upgrade, node maintenance or rolling restarts etc.
You would see something like below for few seconds to few minutes from Management UI:
Any currently supported RabbitMQ.
It is expected and would not impact the cluster and queue operations. The quorum queue would remain available during the maintenance.
It could be ignored. It will back to "running" after the nodes and RabbitMQ process comes back to online completely.
Also, it would not impact the queue availability at all.
We do understand that marking "down" can be scary to any users.
Our team is actively working on this to improve the behavior, to make the entire process more smooth, instead of marking the queues down directly.