In one of the process reports the PV is showing with semi-colon in between repeating the same values again and again.

Do you have a PV of the same name in sub processes?

Yes, Its a CDT that passed into the sub process (passed by reference)

On the sub process node you have under "Setup" an option "Allow data from this sub-process to be included in reports on the parent process model.". Do you need really this?

You may modify the expression in the report to "=pv!CDT[1]" to access only the first item of the list.

I updated the process instance with new values (updating the variable value through designer and saved the process instance), is that a problem?