I hadn't seen this before, cases falling totally off the baked cupcakes.
Hmmm, well I've had paper cases separate from the side of cupcakes before, but I've never seen them totally fall off until this week.
I used red cases to bake a batch of vanilla and a batch of chocolate, then I baked a batch of the same chocolate cake in brown cases.
An hour after baking all the red cases fell off the chocolate cakes, not a slight lift away from the edge, they totally fell off! No problems with vanilla cakes in the same red cases, or any problems with brown cases.
There is a few reasons for cupcake cases coming away from the sides of cupcakes, the main culprit is the brand of the cases. Good cases are made from medium weight paper greaseproof paper, not too wide across the top & straighter sides. Sweden and Scandinavia produce exceptional cases. Fox Run in Australia produces lighter weight papers, but they do stay put. The dark brown cases I use most of time I bulk buy from Earl Craft 'n' Cake inexpensive & reliable, they look great too.
As for the red ones, I guess I'm won't baking chocolate cakes in them ;)