Hello,
Have you tried using SAP_PP_022 Multilevel planning of individual orders.
This heuristic enables you to carry out multilevel planning of an order, taking into account the low-level codes.
The system uses the heuristic that you have assigned in the Heuristic Settings for Multilevel Planning.
If you are changing any master data for finished product then try to use below heuristic
SAP_PP_021 New explosion
Regards
Ashutosh Shende