A product with the ID xxxxxx already exists

Dear Experts,

System is throwing the above error, while replicating material from ECC_NEW to CRM system.  The reason behind the above error is;

We have switched ECC_OLD backend to ECC_New system with CRM (Existing) system. Material which are already existed in the CRM system, those are downloaded from ECC_OLD system. After changing the integration from  ECC_OLD to ECC_NEW

System, while replicating the material system is giving the above bdoc error.  I want to re down load existing material because there is changes in material group 3 and Tax classification.

Please suggest me to overcome the above issue.

Regards

Ashwini