A fix was suggested here: https://discussions.apple.com/thread/251814420

One issue I found is that it didn't work if I tried to set the first frame as the poster frame. All the others worked instantly, but not the first one. Also helpful to know is that by default Apple will set the poster at 5s into the video.

One workaround I had the most luck with is to run the iOS target on the iPhone the watch is attached to, wait for it to install on the watch (check for progress in the Watch app) and then run it manually from the watch. There's no debugging this way though.

One workaround I had the most luck with is to run the iOS target on the iPhone the watch is attached to, wait for it to install on the watch (check for progress in the Watch app) and then run it manually from the watch. There's no debugging this way though.

One workaround I had the most luck with is to run the iOS target on the iPhone the watch is attached to, wait for it to install on the watch (check for progress in the Watch app) and then run it manually from the watch. There's no debugging this way though.

If you go to edit the target then Run, is it set to Launch automatically or does it say Wait for executable to be launched? It might be that you need to launch it manually.

Thanks for posting this, it's helpful.

Clearing cache fixed it for me.

There are some interesting solutions proposed here: https://stackoverflow.com/questions/43819455/xcode-not-displaying-compile-errors I managed to fix it by using DevCleaner from the app store to delete everything.

I can confirm that with newer versions of iOS it's pickerView.subviews.last. You can set its backgroundColor to any color, including clear.