As another data point I've replaced the camera lens and the glass backplate on my 2. The lens went fine. The glass is something like 0.25mm off in basically all dimensions (height, width, thickness). I can feel the transition when I miss the fingerprint sensor. So 3rd party replacements are "okay." This isn't a huge issue, just annoying since I recently replaced it.

Other than that, which I'd call self inflicted since I've had the phone for years and dropped it a few times and hike a lot, I've had no issues. Maybe the 2 had better QC?