I think it just assumes it’s blocked if can’t get any image for a certain amount of time. I had siniliar issueas on darker roads here in Switzerland. Comes and goes though and everything still works fine. Don’t think it can differentiate between darkness and obstruction.
Just got my Model Y with Hardware 4 this week, interested in seeing if that makes a difference as visibility in low light seems to be a ton better than on my HW3 Model 3. I‘ll let You know if anything changed :-)