Symptoms
There is a parent workflow calling the sub process. There are some instances where the parent process is active and it shows that the activity to start the Sub Process has been completed. However, the sub-process is not listed and the operation is not getting completed.
Diagnoses
Enabling Debug-level logging found that the issue was an error at the debug level indicating that the IPC process was unable to start because the input was not in the correct format. The issue occurs when users submit the form without making any changes to it.
Resolution
Disabling the button until changes occur solves the problem.