Problem with Matrix and measures total (group)

I have a problem calculating totals in matrix.
There is 1 table history with all movements +/- of articles with a purchase price. I only need the last purchase price multiplied by the total + or - of the correct item.
This will work. I am getting the correct amount of quantity in stock * last purchase price via DAX

These articles are linked to a group, but I can no longer make a total sum per group of articles. The Group total is not correct. When Single item (1 article) is present in the group, the total of the group is correct calculated.
The grand total is also not correct calculated