It's good to know that "Reset All Content and Settings" works, thank you for that answer! But I want to test this, and I'd rather not delete my entire iOS device! Also, I'm a little concerned about what this means for the experience our existing users will have once ATT goes live?

I'm having almost exactly the same error (different pid value and different number after XCodePreviews). Also using XCode 13.0. This is in my main project, and previews were working, albeit sporadically, until a couple weeks ago.