In my Homey Pro setup, my entire lighting in the house i consolidated in a Philips Hue bridge, managed by the Homey.
At random times, sometimes a few times during a day, other times days inbetween, lights are loweredd to minimum level (appr. 10%) - all over the house at the same time.
Lights can then be reset to preset value by double-tap on the corresponding switch or in the app.
This is an old issue by now, and I have asked about it before with no resolution, so fingers crossed.
I actually had the same problem a while back. In my case it was a Hue Motion sensor thar caused the problem. Whenever the Hue Motion Sensor was activated/deactivated it took approx 4 minutes and all my Hue lights dimmed down to 0%. It started with 2 Hue-lights, but in the end all Hue-lights where affected. This is not a Homey-problem, but a Hue Bridge problem. I resolved it by removing the Hue Motion sensor from the Hue Bridge (and Homey) and exchanged it into a Z-Wave sensor directly to Homey.
Yeah when you know at what time strange things happen, you can check the log file entries and look for the lines with matching timestamps, in order to find possible explanations for the ghost events.
In the app settings / app configuration, you can temporary select “Debug” level. This records the most events possible, but generates biiiiiigg files as well. Select “Info” or “Notice” when there’s nothing to troubleshoot.
It creates a log file each day. This file can be downloaded by longpressing / clicking the file name of today, or yesterday or earlier dates.
What’s in there? Something like: