This is an issue for me almost every day. I have to drive around sunset, and it's quite bad both for me and for FSD in the interval between about 20 minutes and 5 minutes before sunset. A couple of times, I've had it simply stop when there is a green light but the sun is exactly behind it and it's very difficult to make out. This is obviously very uncomfortable when it happens, and it's hard for me see also and decide everything quickly enough that I should override it.
At some point I'd like to do a comparison to see if HW4 front cameras can deal with the direct sunlight any better.
In addition, this depends strongly on the cleanliness of the windshield, both inside and outside surfaces, over the front cameras. Back in September I was having a great deal of trouble, with FSD frequently refusing to continue with low sun. Looking at dash cam clips, I could see there was an absolutely horrible flare problem even after I cleaned the windshield outside surface. Kind of scary really, when you looked at the video recording.
So I did some searching online and figured out how to remove the camera housing over the rear view mirror, then cleaned the glass with isopropyl. My car is parked outside and gets direct Arizona sun many hours per day, and there was a significant film/haze on the inner glass over the cameras. I saved dash cam clips of my sunset drives in the days before and after this cleaning procedure, and it made a huge difference (much better but not flare-free after the cleaning).
I have to assume that Tesla is quite aware of this, but it rarely gets discussed. I think there should be some AI-trained recognition of notable flare from sunlight, headlamps and street lights at night. Then the owner could be informed of the issue and schedule a service. I also think they should redesign the camera housing to be much simpler to remove for cleaning the glass. It's not a small issue and most people never think about it.