Process builder error

Hi Trailblazers receiving below error can anyone please explain  why i am getting this error. 

Challenge Not yet complete... here's what's wrong: There was an unexpected error in your org which is preventing this assessment check from completing: System.DmlException: Insert failed. First exception on row 0; first error: CANNOT_EXECUTE_FLOW_TRIGGER, We can't save this record because the “opportunities for any prospect account or customer account” process failed. Give your Salesforce admin these details. This error occurred when the flow tried to create records: FIELD_INTEGRITY_EXCEPTION: Assigned To ID: id value of incorrect type: 0015j00000Xw4LBAAZ. You can look up ExceptionCode values in the SOAP API Developer Guide. Error ID: 273510618-78858 (157788690)look up ExceptionCode values in the SOAP API Developer Guide. Error ID: 273510618-78858 (157788690): []

Help will be greatly appreciated. 

Thanks Amit