Hi Jelena,
I actually did check a few SAP notes but to no luck.
I referred mainly to SAP note 570391 and 716141, but was not able to spiral in on one reason valid enough to be causing this. I had also referred several SCN posts regarding RVKRED07, RVKRED88 and RVKRED77, to find little about this particular issue that I am facing.
Looks ABAP walkthrough is my last resort, since the calculations are complex we had given up in between once when we sat through the same.
It would, as you can guess, have helped a lot if someone knew the root cause of this issue.