I caved in and bought a new replacement Rev G cabin camera off eBay for about $140 to replace the original 1098383-00-D camera that came with my 2018 M3P. I just installed it this morning, and guess what... it solved my problem! My wife and I went on two long FSD drives tonight after replacing the camera and did not experience a single "Cabin Camera Unavailable" error that would normally kill FSD. As mentioned previously, I would normally get a 'cabin camera unavailable' error within the first few moments of every drive, but this new Rev G camera seems to have done the trick. I'm going to continue to monitor the issue and I'll provide an update later this week after I get a few more drives in. But as of right now I'm considering it solved. Seems like a worth while solution for others to try if you are willing to do the work.
FYI... removing the trim around the rear view mirror was an absolute pain. The YouTube videos make it look so easy, but both the small trim piece as well as the larger shroud were attached via the clips extremely well. I was afraid I was going to break it, but eventually got it. Anyway, you'll need a good, small, L-shaped pry bar to release the larger shroud the first time. Also, I've been on 2024.3.25 for a while now in case people are wondering about SW version.
FYI... removing the trim around the rear view mirror was an absolute pain. The YouTube videos make it look so easy, but both the small trim piece as well as the larger shroud were attached via the clips extremely well. I was afraid I was going to break it, but eventually got it. Anyway, you'll need a good, small, L-shaped pry bar to release the larger shroud the first time. Also, I've been on 2024.3.25 for a while now in case people are wondering about SW version.