R3483 - MRP in not explode down correctly messages por raw materials

Im working with MRP - MPS - DRP (R3483) for multiplant.
first the forecast is uploaded in a branch named "C", after it gets a branch known as "B" which only is used for transfer and the other branch is "A" which manufactured items.
A (manufactured) → B(distribution) → C (final distribution branch)

the data selection include .
Planning code =1
Branches = A, B, C.
2nd item number = Finish good which gets records of forecast.

when i run R3483 ( set up as generation type single level MPS-DRP).
on tab horizon it considers 36 months.
on tab parameters it gets generation mode =2.
Generation type =1 (single level)