We have a very simple fast query that works fine in Sitecore Authoring instance but returning null on Delivery instance.

The issue was solved by Rebuild Descendants using DbCleanup.aspx page in Admin folder:

This also means that this probably has nothing to do which instance it’s on.

I am thinking this has something to do with how we installed the items using WebDeploy packages. It converts Sitecore package into SQL DacPac and inserts items into SQL database directly. There must be some chained actions that are not triggered when it’s inserted directly into the SQL databases.

We have encountered issues with Publishing Service as well, haven’t be able to test this, but highly suspect that this should resolve Publishing Service issues as well.