I myself is an MM consultant and working on workflow too
I experienced a strange thing that: when I map the creator ID in workflow as approval ID then it worked fin
like creator ID is ABC and i put the same ID in workflow in PR release strategy configuration, then it worked fine
Additionally, since it was QAS therefore I didnt configure RFC from wf-batch so i can see that only in creator's ID, swuf is confiured
.
But for approval ID, its not configured 
This is the creator ID from which I initially configured RFC
THIS is the ID of approvar authority
