Can you check if there is a situation where there are tasks pending in that queue while one of the workers is idle?

In what queue ? In services there are no pending tasks because they were all pulled by 'training'.

just to maker sure, how do you start the agents? Are you using the

--services-mode

option?

I used clearml-agent daemon --detached --services-mode --queue services --docker ubuntu:18.04 --cpu-only