I am running hundreds of jobs on a Windows 10 workgroup and having issues with many jobs being "killed by ?" . And that text is exactly what is in the log including the '?'
The stdout of the job itself says it received a signal to terminate.
This is quite odd as the machine the job was running on is a headless machine with the following local configuration file.
use POLICY : Always_Run_Jobs
WANT_SUSPEND=FALSE
WANT_VACATE=FALSE
The starter log says
01/02/20 13:28:35 (pid:29744) Create_Process succeeded, pid=31732
01/02/20 13:48:28 (pid:29744) Got SIGTERM. Performing graceful shutdown.
01/02/20 13:48:28 (pid:29744) ShutdownGraceful all jobs.
01/02/20 13:48:29 (pid:29744) Process exited, pid=31732, status=-1073741510