I have set a label corner radius to 18. When I launch the app in debug or release , I can see it transform from 0 radius to 18 although I have set it in designer also sometimes it keeps the round corner 18 but sometimes it changes to 0 radius and stay that way.
I guess that it is a similar issue as the labels background color that sometimes disappear. It is related to the way iOS handles labels. Use a transparent label and put it inside a panel with the background and border you want.