This can have various causes:
If you switch the spotlight manually
If you have programmed timers
If you have programmed SMART automations that switch the spotlight
If you change the spotlight settings (e.g. brightness or color temperature)
If you want the spotlight to remain on sensor, you can create the following automation under the “SMART” area:
If: Spotlight mode Manual
Then: Spotlight mode sensor
If you also want to switch manually from time to time, you can add a delay:
If: Spotlight mode Manual
Then: Delay the action for x minutes
Then: Spotlight mode sensor
Translated with DeepL.com (free version)