The similar issues with the same error were reported before - e.g. T133213: [betalabs-Regression] 'Browse topics' "[FLOW] Rendered topic not found when attempting to scroll" and T114138: 'View and restore deleted pages' displays 'No topics returned from API' . I will look again to see if the issue became more specific and/or more severe.

Reproducible (though a little bit tricky): 1) a Flow board should have quite few topics, so 'Browse topics' should be scrollable 2) when a topic is clicked, and a user is directed to it, continue to scroll 'Browse topics' and, then, click on another topics.
It does not seem to be specific to a) Flow board b) Flow topics c) the status of Flow topics
per @Mooeypoo, most likely, it's caused by the fact that the selected topic is not loaded in time after the topic title was clicked the topic title in the 'Browse topic', hence 'no topics returned' message. Should be more noticeable on the slower network connection.

e.g. on Talk:ET1 which has lots of topics.

1. From 'Browse topics', click on one of the resolved topics (not at the top of the list)
2. When you'll be taken to the topic, scroll a little bit up quickly - often "Database query error" is displayed.
3. Do not change your position on the page, click on 'Browse on topics' again, select 'Rs9k21e73g' topic, the following error will be displayed.
   
   [FLOW] Rendered topic not found when attempting to scroll!