I agree, we have been fighting this issue since upgrading to E10.1.600. Support gave us two “fixes”. SQL fix to run on the database “This fix program goes through the given tables and updates certain fields that are not the same case as the fields on the table where they are a primary key”. The other is a trailing spaces datafix. Both helped but we have to run those each time before we run the report to get an accurate number.
You will also have this problem with the Slow Moving Stock Report but this one also seems to be fixed in 10.2.
If I were you, I would report the issue to Epicor if you haven’t already. They haven’t given me an sense that they are working hard on fixing this report (on the 10.1 version) that our managers use to make business decisions. They just gave me the fixes and sent me on my way. The more people report it, maybe they will get their act together. Depending on the cost of the part that is missing, you could have a severely inaccurate report and you may not even know it!