Hmm I might need to double check my manual again. I have a moultrie M880 and I an pretty sure the sensor will detect out to 40 feet. I know the IR illuminates out further than that during nighttime shots.

Obviously the camera can pick up nice detail of objects well outside the sensor range when it gets tripped.

As far as what you've described during the setup, I had a similar experience to when the light would go on and off. It was consistently at 40 feet, which was what i expected based on the product descrition. However it was a little bit confusing determining when it had and hadn't sensed me in certain situations.

So I think that there might be some delay in the LED telling you it sensed you, or possibly a timeout period between LED flashes.

I learn to test the left and right outside edges of its 50 degre fov, and then then perimeter of the 40 foot detection range.

I've only been running it for 2 weeks and the first set of pics turned out nicely based on how chose to set it up.

But again check your manual, I don't know if we have the exact same model, But I know mine doesn't detect motion at 100 feet. Pretty sure it's right around 40