Description: 

The customer has enabled the new navigation for all users on the site. However, they are still experiencing the old navigation interface, and a few pages still use the old navigation.The new UI is enabled at the site level and also on the Space level.

Some pages are not adapting to the new navigation  

It seems that pages that are migrated from Server/DC but haven't been published (updated) on Confluence Cloud (these will have a null editor property) are not adapting to the new navigation .