That's quite a contrast you have there with the bright sky and the dark silhouette of your trees.
It's likely fooling the light sensor before switching to IR mode.
Do you also have IR mode set to come on based on light conditions?
Could it be the changing location of the sunset has caused this issue that wasn't there in the summer? And if they are cameras that have been there years, perhaps the direct sun at those angles has degraded the sensor over time.
It is best to set up a day profile and a night profile and use BI to switch between the two and then have the parameters dialed in for day and night.
You would set the Night Profile to be forced B/W instead of auto and then it will kick in earlier.
It might not be an option.RE: Do you also have IR mode set to come on based on light conditions?
No not sure how to go about that?
not sure how to set up profiles?
It might not be an option.
Your screenshot from earlier shows the Day profile.
There will also be an option for Night.
Yeah if you set the day one you're probably setting for dawn not dusk.
If it's still not working try Wittaj's suggestion above of setting a day night schedule via BI. It's a proven method. From memory I believe most set the changeover 10 mins before sunset but probably Wittaj could confirm.