Error in customer mass change

Hello,

we are trying to update a customer with mass change process and getting below error.

"50000346 of entity type Bus. Partner ID is still being used for value 50000346/4222577/BUR001 of entity type Relationsh.Cat."

This customer has relationship created as "has contact person" but in mass change we are updating "Central Data" entity but no contact person fields are involved in this.

Anyone has faced similar issues previously?

Thanks

Ninad