I'm running into the same issue and I haven't found a good workaround — other than removing the NavigationView, which requires a lot of additional work...

Hmm... I'm still getting the same issue ("Unable to load") with my widget on Xcode beta 3 even if I remove all my widgets and add a new widget. It doesn't even work when I delete the app from the simulator/device and reinstall. Did you need to do anything else to get it working on beta 3? It worked fine with beta 2.