We are seeing similar issues. Our state values are also coming back incorrectly within the .sheet block. Most peculiar! Notable: changing from a sheet to a popover allows our code to run again. Definitely feels like an Apple bug. Let's submit radars! (FB8689560 here.)

We are seeing the same issue here. Our library's SwiftUI preview stopped working as soon as we included another library. :(

We're seeing something very similar in our app; still trying to run it down. John, how on earth did you figure out that your UIColor extension was triggering this behavior? :P