I am using ES6.2 (on elastic.co) and I have a giant search query that has many in-line painless scripting. And in that search query, I have "explain": true to see the result scoring explanation. Most of the time the search result returns explanation, but for the same query with a specific set of different search parameters values, it doesn't return the explanation while it returns the search result correctly.
Is it a bug in ES itself that explanation disappear for some reason? Or do I need to do something to get explanation back consistently?