Movement Detection Query

I am using motioneye to monitor my roofspace to monitor a known source of water ingress. I have the set minimal the thresholds as low as I can but I am not convinced that I am catching every movement that is detectable. Not least because I can see water dripping outside the red bounding box in the debug in an area that is not masked off.

Any one have any suggestions to make this more sensitive in this application?

Motioneye 0.42.1 Motion version 4.2.2 OS Raspbian10 Motion settings: Example video capture and debug

https://user-images.githubusercontent.com/189524/135128399-ffb720f8-de93-48c6-8340-27d302c263ac.mp4

https://user-images.githubusercontent.com/189524/135128421-7839d48f-8a5d-46d3-862e-728c10fa8200.mp4