@schunter1969 - those are almost identical to mine, but at night in BI, I'm running 100 min object size and 20 minimum contrast at night.
Do you have an SD card in the camera that you could pull a few night pics from and post here?
With BI there is some "calibrating" for LPR because the screen is so dark at night. I run two settings and the night setting I run the min object size and contrast different than the day settings. I suspect that you will have to run a smaller min object size and maybe less for contrast.
At night, all the camera will probably see is headlight/tailight and a plate, so the min object size needs to be small, like the size of the headlight. What I did was had a family member take a car out to the spot and had them stop long enough that when I pull up the motion configuration setting menu I could size it to the headlight.
I also suspect because it is such a dark image at night, you can take that min object size down really low because the camera will not see anything else. Obviously need it larger during the day so that every leaf doesn't send it off.