re:
Its back to mormal now. Comments are now showing up.
Edit: Ops, maybe not. Its a hit-or-miss ordeal.
Well, it took me a while to get the pattern, but it's not a hit/miss. It's been bugging me for ages now.
Anyway:
1. I post something in a private group i have
2. You comment - notification works and takes me there
3. Someone else comments and the notification leads to data error
4. If you're lucky to get another unrelated notification, you can tap the first notification you got about the post and it and ONLY it will work and get you to your post. If it groups your notifications - you gotta walk over there.
I have not tested if it has to do with where the post is since i use fb for a small array of things, but try it out. Maybe you'll figure it out