Incorrect calculation in the Cost Component split in 12 Currency Type

[Team]

Dear colleagues,
We have one issue with Material Ledger where we need your support. There is an incorrect calculation in the Cost Component split in 12 Currency Type in our system.
The main issue is that the Cost Component split in ‘12’ Currency Type is not equal to ‘10’ Currency Type. To be clear, in our solution we activated ‘12’ Currency Type just in case. We don’t use Profit Center Accounting and according to Blueprint, the sums in ‘12’ Currency Type has to be equal to ‘10’ Currency Type. 
We investigated that case by ourselves and found out that the difference were calculated due to PP-order Settlement. 
 
For the first sight, the reason is that the system calls functional module ‘CKMO_GET_ORD_HIST_MLCCS’ for ‘10’ Currency Type, and it’s not the same as for ‘12’. The systems calls functional module ‘MLCCS_KSTAR_TO_KSTEL’ for ‘12’ Currency Type.

As a result the cost in ‘12’ Currency Type calculated according to their own principles and not equal to ‘10’ Currency Type. PP-order has absolutely the same amounts in ‘10’ and ‘12’ currency during the period. There are no additional FI documents posted to change the sums in ‘12’ Currency type. Actually after analysis we can confirm that there are no reasons the sums in Cost Component splitting in ‘10’ and ‘12’ Currency Types to be not equal. But we see the opposite situation in the system.

Our question is what the reason that the sums in 10 and 12 Currency types are not equal in that case?