Different people do the research in different ways. I start by opening the mobile app, going to rooms, selecting things, finding one of the lights that I know had the problem, and clicking on the name of that light (just the name, not the icons to the left or right of it).
This will open up the detail page for that device. Tap on recently at the top of the page and you will see the log of events for that particular light. That might immediately tell you if there was a particular smart app involved.
After that, you can start digging deeper into the logs that are available under the developer tools. The following thread explains how to do all of that: