Reassignment not inherited in PO

Hi:

We have fixed wrong commitment items hit at PR usinging FMCB and FMCT. Now i am facing a issue. A PR whose commitment item was A and we changed it B vis reassignment. When we create PO with reference to Reassigned PR, system not inheriting PR commitment item, instead it is calling from FMDERIVE.. Is there a way to aboid it , fixing derivation rules is last option ..

Regards