When you get this error you have duplicate product code within Lightspeed. The EAN is a SKU or product code that has no stock level as that is all managed inside BRM. 

The exact message is "More than one item matches itemCode"

Note that this error comes back from the BRM call to Lightspeed so it is a Lightspeed configuration issue.

See in this Lightspeed configuration article how to manage the codes.