2 of the bounce servers get stuck on cron-running


Hello. Once again I have been notified that 2 of our SMTP servers have stopped reporting bounces. I look at the bounce servers and see that once again they are STUCK on "cron-running".
Why would that happen many times? Is it a setting on the back end? I don't think they are set up any differently than the server that doesn't get stuck.

Can anyone tell me what might be wrong?