Ago function cannot show the correct data

Question

I created a logic columns to get the measure of last month. No error occurs but only get the unexpected data.
Dont know why. Any advise?
Logic column: Count of Last Month=ago("TEST"."Fact Transaction"."Count" , "TEST"."Time Hierarchy"."Month" ,1)
Result:
Month
Count
Count of Last Month
4
77
0
5
130
130
6
240
240
7
180
180
8
220
220
Time Hierarchy:
Total->Year->Quarter->Month->Date->Hour->DateTime(key of the time dimension table)
Ticked the 'Time Hierarchy' and set the 'Chronological Key' for each level.
Have to mention that I created 2 Hierarchies for the time dimension table. The 2nd hierarchy is as below:
Date Hierarchy:
Total->Year->Quarter->Month->Date

Answer 1

Seems it's caused by the 2 time-hierarchy. I built 2 time-hierarchy on one table, one has the week level the other doesn't. When I removed one, the result is correct.