This problem still exists with Xcode 12.4 !

This seems to get ridiculous: we're all in home office and Apple can't make sure the internet connection stays stable? All I read here seems not to fix this problem and the checked solution is the sys feedback page from Apple - posted 6 months ago? I have 4 Macs and those running Big Sur have these unstable connections. The one with Catalina does not. Apple, hello? Anyone home?

This will deselect all annotations, which have been previously selected. let selectedAnnotations = mapView.selectedAnnotations for annotation in selectedAnnotations {       mapView.deselectAnnotation(annotation, animated: false) // better to animate selection, since deselection could be many }

This helped a lot.I missed just this line, because I had wrapped the options in a var and forgot to finally apply the option to the "cloudStoreDescription".cloudStoreDescription.cloudKitContainerOptions = NSPersistentCloudKitContainerOptions( containerIdentifier: "iCloud.com.mydomain.mycontainer")