I have a job that starts a ssh-agent:
[ssh-agent] Looking for ssh-agent implementation...
[ssh-agent] Exec ssh-agent (binary ssh-agent on a remote machine)
$ ssh-agent
SSH_AUTH_SOCK=/tmp/ssh-iJL2AkutZ8Xm/agent.27447
SSH_AGENT_PID=27449
[ssh-agent] Started.
Sometimes, the process of the ssh-agent dies during the job execution (the job runs during a couple of hours).

When terminating the job, Jenkins tries to kill the ssh-agent, but this fails
$ ssh-agent -k
kill: No such process
ERROR: Failed to run ssh-agent -k
This makes the job fail.