Ok got it. My assumption was , we can have same process (same process key ) in multiple process applications as long as their content remains same, which was totally wrong. There is a similar post to this Ref:- Process Deployments with failing startup of process application - #14 by thorben.
Anyway I will remove the common reusable processes from one of the war. Thank you @Niall for you detailed response.
Regards,
Prasad