I’m sure that’s frustrating! I would definitely contact support@smartthings.com if you haven’t already. There are things that they can look at from their side which may help diagnose the problem.
Meanwhile, If you want to look at the logs yourself, each device has an event log in the mobile app.
Open the mobile app and go to the rooms section (icon with 4 little squares in the bottom row).
Choose “things” at the top of the page.
Click on the name of the device you want to check (not the icons on the left or right of it, just the actual text name), and you will open its details page.
On the details page, click “recently” at the top of the page and you will see the recent events for that device. That should tell you which smart app, if any, activated the device.
If you still need more information, you can start digging into the system logs: