parallel processing + "Maximum number of SAP GUI sessions reached"

Hi all

I have implemented a parallel processing logic inside a report using FM SPBT*.Everything is working fine in dev and qas system but in production system. I received pop-up "Maximum number of SAP GUI sessions reached" multiple times.

I have checked RZ12, system profile everything is same. The only difference is that in production system there are 2 lines of same logon group,which are not called as parallel_generators, but difference instance. Max session is 6 for all of them.

I have checked this post but it is out date for my system. https://answers.sap.com/questions/12238933/parallel-processing-maximum-sessions-error.html

I am looking forward for any help and suggestion.

Thanks