I just posted this: https://developer.apple.com/forums/thread/737819 Yes, during Open Water Swims, GPS performance on the ULTRA has degraded severely. We have several users now reporting that the GPS tracks produced during Open water workouts with either built in Workout OR with Open Water Swim are now largely unusable. I have confirmed this with my own swims as well. I would appreciate an upvote on my post as well. BTW, the issue is identical for the built in Workout app during open water swim.

I'm not sure if you are using it for open water swimming, but it may be related to an issue that I have described in detail here: https://developer.apple.com/forums/thread/737819

I have found the following to work: from your phone, remove the watch app by toggling the "show on watch". If you have a watch only app, delete the app from the watch. That's it, you should now be able to install and launch the watch app from Xcode.