The Collective Cocktail Shaker

This cocktail shaker is absolutely gorgeous and makes a great edition to any bar cart, cabinet, or display. Please make sure you secure the lid properly and shake away!

My son in law made us some delicious cocktails for New Years Eve using the beautiful cocktail shaker. However, it was near impossible to open up for the second drink. The lid could not be budged, until we ran it under the tap and warmed it up. What is going on with this?