One thing I learned from doing professional camera installations in places like Home Depot and such... remove wasted space out of the image. Do you need to see above those houses in the background? Lower your camera. I placed a 6' ladder infront of my house to where a human would walk. That is near the upper border of my camera image. Is your camera catching too much of a side wall? Re-angle it as this will also help with IR backwash. The point being...why include static non-critical imagery on your camera as it is wasted space.
Now, what I may not understand or have a grasp of... Blue Iris
or camera AI itself, does things get less sensitive as you move away from the center of the lens? I use on board camera AI for IVS tripwires and such. I think at night time, it does have more issues of false alerts the further from center point the alert happens. I have to test more on this someday.