Activity chaining

What error is the process model throwing?

please include additional information and the relevant code snippet.

Need more information on error that you are getting. And I would suggest you to look into tomcat logs to see what's breaking it

What do you mean by breaking?
Are you not able to see the tasks or any error is displayed in UI or process model?

As all 3 prior commentors have noted in various correct ways, you need to provide quite a bit more detail here if you hope for a meaningful answer.

1) info about your setup; 2) what you expect the user to experience (and why); and 3) what's happening wrong in your opinion and why you believe it's wrong.  Just for starters.

can u please keep more explanation on that ? what are you mean by that breaking?