When I read your post, I was thinking about how Billerica revamped 3A/Boston Rd around the town center and how that might impact mapping and FSD behavior. tbh, i haven't been putting a lot of mental power into tying FSD behavior to potential mapping issues. I just disengage whenever the system does something stupid.
As you know, I did dig around OpenStreetMaps a bit, since there seems to be a popular consensus that some mapping data may be sourced from there, but so far I haven't found a smoking gun tying incorrect/missing data from OSM and FSD. That doesn't mean there might not be a problem with Tesla's map, but I'm not sure we can do much about it except report the issue.