This is still happening for me in 2022 on WatchOS 9. It works on a physical device but not any of the simulators. I had to add this to my WCSessionDelegate on the apple watch controller func session(_ session: WCSession, didReceiveMessage message: [String : Any]) {     }

I have not, should i do that through Feedback Assistant?

This is happening on all iOS 15 apps. Open the app Close the app and quickly reopen. This will cause the app to crash if you do it fast enough. It seems to work as expected if you wait at least one second before reopening. To resolve this issue close ALL background apps so the "recent apps" are empty. When you do this, the problem in step 2 does not happen. To "re-activate" the crash, open 5 to 10 apps and put them in the background. All apps will then continue to crash when re-opening.