I always disliked the word ‘motion sensor’ in these devices…they are simply infrared sensors tuned to body temperature. I have a couple on my font porch and when people are bundled up in jackets and gloves they could move around all they want and would never trip the motion sensor.
as @nathancu mentioned, the heat change may be your issue. I have found that sensing motion inside my house is a waste of time. Mostly because pets tend to set these off. Instead, I would focus on glass sensors and open close sensors for the doors to alert on when away