When I copy and paste a Caption in the subtitle timeline, it doesn't maintain the same properties. Rather, it resets to the default font, size, position, field size, anchor point/zone, etc. When I add a new caption, it does the same.
Since I've had issues with master styles changing multiple different captions to the same text, I've shied away from using them. Please, fix the master styles feature or let copies of captions be legit copies.