This is a similar question to this but not quite the same.
I have created a subclass of UITableViewCell which references a custom nib and marked it as @IBDesignable. Cha
This issue has been resolved as of Xcode 9.
I had reported this issue to Apple and at least have the piece of mind knowing that this is a known bug. It is currently an open issue under the problem ID 17973876.
Edit: As of 12/7/2016 this bug is still marked as open.