I just realized this last time I played Skyrim. I was playing a Level 40 Redguard Thief with a Level 100 Sneak. Now at first I thought it was just the enemies leveling, since most of the time games with leveling feature would make enemies stronger as you level up higher, but I think it's not the case. Back before I was in the Dark Brotherhood missions I used to be a ninja. I can even sneak up in front of people. Usually all I would do is get into a higher spot where the enemies can't access and I would just arrow down the enemies while sneaking without ever being detected and that was at Level 60 Sneak, I can even sneak past a bandit right in front of him while wearing heavy armor. But just recently, once I've finished the Nightingale quest I noticed that I've lost the ability to sneak! It's really annoying since I play the game stealth style all the time. Is there any way to fix this? It seems that once you reached a certain level or finish a certain quest some skills just reset or bugs out.