I had same issue with hue motion sensors and figured out why this happens. Hue motion sensor waits clear message until it again detects motion. If lights go off and you step in before the clear message then the clear message wont come until you stand still or go away from the room. Then after 10s the clear message will come and it detects motion again. So basically you can stand under the motion detector a day and it will not do anything.
Not sure how to “fix” it yet.