For iCloud Container Identifiers you have the name of your database and for iCloud Services just cloudKit? I have both of these set and have the same issue that you originally posted about, not reliable – sometimes it works, sometimes it doesn't. Curious if you have made any additional discoveries? Super frustrating!

For anyone stuck on this (as I was), my issue was that I did not change my imported framework in my extension from "embed and sign" to "do not embed". Changing this ensures everything builds but does not include the nested framework in the bundle which generates this error.