The error happens if the Company Name or other field on the customer record is used as a reference key when updating customer record.
There are only 3 reference keys that we can use when updating customer record. These are the Internal ID, External ID and Customer ID.
Note: Error 'Matched more than one record' will be encountered if :
1. The customer record that is being updated has a parent customer with several child customers.
2. Data Handling used is Add or Update.
3. Child of is mapped.
4. Either Internal ID, External ID or Customer ID is not mapped.
Note: Enhancement 189143 was filed to be able to import file using the company name as reference key on the mapping.