The exit code 20005 is not an AutoSys specific exit code. Usually this type of exit code comes from a script/command or the Operating system.
On Windows, use the command 'net helpmsg <exit_code>' for explanation of the error code.
On Unix the meaning of error codes can often be found in the file /usr/include/sys/errno.h
At times we have had clients stated they saw those types of errors when permissions or access to a file/command was in some way compromised.
Meaning they did not have access.
Review the job's std*files, the agent logs and operating system logs from the time of the problem for additional information.