SHELL’IT BE OPEN OR CLOSED?
If they are fresh and you trust the supply chain, open mussels before cooking probably just means they’re still alive. Closed mussels after cooking could be that the muscle didn’t relax or was pushed closed during cooking. It doesn’t mean that these mussels can’t be served, before discarding test by comparing these mussels to the others on smell, colour and texture (sensory). Squeeze live mussels to see if they close, cooked mussels can be set aside and forced open to compare.