Hi,
Can you please refer the following SAP KBA Note and check whether it helps you:
1786451 - Value of a characteristic is not converted - BRAIN068
Also, please refer the following SAP Notes and check whether it helps you:
454004 - PSBW: PROJ and WBSEL conversion exit
1691454 - Conversion exits PROJ and WBSEL may not work as expected
1472620 - PS-BW-Checkman Solving -Conversion Routine
Thanks & Regards,
Sapna