Looking at the 2nd image you sent, I see that in addition to "services" queue, you also have queues called "training" and "training*_2" - and the experiments you circled is in the "training" queue. In that image - there are no experiments in the services queue.
If you press on the "services" queue (like you did in the first image) you can view the experiments in the queue and the workers. Can you check if there is a situation where there are tasks pending in that queue while one of the workers is idle?