Can a job in STARTING status but is waiting for an available initiator on the agent side be force completed?
The default initiators is 1000. The WA Agent can concurrently run 1000 jobs. The "waiting for initiators" message indicates that agent has used maximum number of initiators for jobs. Each job will use an initiator and it is returned or freed up when the job completes. Long running jobs and file monitoring will use an initiator for a long time. This will sometimes result in WA Agent in out of initiators.
Users may temporarily increase the number of available initiators for the job class on the agent side. Edit the agentparm.txt file on the agent machine and increase the initiator value:
Restart the WA Agent once the parameter has been increased. Once the agent is restarted, the jobs will start executing.
Note: It is recommended to increase the default initiator class by 100.
Here is the documentation link with more details about initiators.