There seems to be something strange about Windows EWS - its bubble doesn't show up at first, and when it failed to build, it went purple instead of orange.
I think that I know what it is, it's a bug in Attachment._calculate_queue_positions.
all_work_items = WorkItems.all().fetch(limit=len(Queue.all()))
This only fetches as many queues as we have configured now - but we've deleted many queues, and they are still in the table. So we fail to fetch work items for some queues.
Created attachment 238962 [details]