A want to clearify one thing that is very plausible, I haven't the data right now, but I think to remember that the negative stocks in FI were only on those materials also in MM, but with different ammount in FI (less). These could lead me to the point that for those materials the related initial stock were in archived materials in FI, so this could create those negate balances in FI.
For the other differences, on MM materials also in FI, but with no initial stock the reason could be another one, maybe those differences are in the "no materials" values in FI. But I am conjecturing, Im not an expert in MM.
Please if somebody knows which can be the reason of this issue, and help me to focus my work.