Material replication issue from S4 system to C4C

Dear Team,

Material replication is working fine from ECC to CRM system but same material replication from S4 system to CRM is not working.

getting error in crm inbound queue is "Data was lost while copying a value." as BDOC not getting generated in CRM system if source is S4.

I have debugged the queue and I found that Mat_guid is empty . Can you please help me how and where this mat_guid data get filled from table comm_product.

Thanks and Regards,

MD