Using standard GardenWorld database
A product, i.e., PChair with setup for all price (list/standard/limit) to be Zero.
Step to Error
Create a Sales Order / Sales Order Line
In Sales Order Line, select PChair, note that all price is Zero.
Change UOM to 6-Pack. Note that, Qty Entered = 1, Qty Ordered = 6
Now, you will see the UOM reset back to "Each" but Qty Ordered is still 6!!!!
From here, if you enter the Price, the calculation of Line Amount will be incorrect.
Standard Window 7 + Postgres