For once, I also encounter your problem for a new COSC certified watch. Mine lost even more than yours, about 30mins per day, sent for authorised SC they regulate it and then back to COSC accuracy. I'd say as long as modern ETA / swiss movement or any in house caliber, their accuracy really doesnt differ much even with or without COSC certified. As time passes, mechanical movements tend to gain or lost more time, a simple regulate service will do.