Whenever I make classic size cupcakes a good amount of the liners, for lack of a better term, "buckle" in around one or more of the sides. In other words they do not stay round and flush up against the wall of the baking tin. So I don't always end up getting a nice round looking cupcake. They will have in indent on one side or more. Is there a trick to this or do I need to find better cupcake liners? I don't mind this happening if making cupcakes for my family but for a client I want them to look perfect. I use classic size cupcake papers. Right now I have 2 different brands in my kitchen and they both do the same thing.
Pay attention to the size of the liners vs the size of your baking tins. There are different sized liners so be sure you use liners whose bases are the same size as the cup you will set them in. If I use liners that are too big for the pan I get buckling papers too. So I am careful now.
I have found this happens after I have a package of baking cups that have been opened. I think they flatten out too much and then don't want to set in the pan right. I've started putting all of my extra cups in a bowl that helps keep them in a tighter shape.