I see the exact same weird class name in a 'purple' warning message when running one of my projects:
Attempting to unarchive Swift class 'AppKit.NSScrollPocket.(unknown context at $19bd29ed8).BackdropView' with unstable runtime name '_TtCC6AppKit14NSScrollPocketP33_EC3F85FAB7755D56E669206D2B17725B12BackdropView'.
The runtime name for this class may change in the future, leading to non-decodable data.
You can use the 'objc' attribute to ensure that the name will not change:
"@objc(_TtCC6AppKit14NSScrollPocketP33_EC3F85FAB7755D56E669206D2B17725B12BackdropView)"
If there are no existing archives containing this class, you should choose a unique, prefixed name instead:
"@objc(ABCMyModel)"
The purple error line is on instantiation of a Storyboard. I have no idea which element in the Storyboard is responsible for this warning, which makes it hard to make an example project for a Feedback.
Do you see the same kind of warning or something completely different?