[OBIEE] Issue with AGO Function

Our aim is to visualize a table having as columns the ID, the production department, this year revenue and the last year revenue. To archive last year revenue we used the AGO function with arguments:

             Ago("Sales"."FattN" , "UPGDWH"."Dim Calendar Delivery Note "."Year" ,1)

1) This year profit;

2) The time level;

3) the offset.

The issue is that the resulting value referred to last year is not correct, as a matter of fact the report shows strange values, they seam random results despite of correct values of the current profit used as argument in the AGO function. With respect to the time dimension, we tried to expose each level of the hierarchy, but the last year revenue remains wrong. The time dimension design was properly defined as well as the physical and logical designs. We tried to exhibit/exclude many dimensions related to our production department, but nothing seems effective. Surfing on the internet we