I'm level 67 with around 180 hours of playtime.

I'm wondering if anyone else has experienced this curious invisibility bug, starting from the stairs inside Jarl Baalgruf's Quarters (Dragonsreach)? This applies to my character and any other NPC including the Jarl himself.

I'm still running the game with the previous update (1.4) on XBox 360. Personally, I'm betting on that this particular bug would persist regardless of any update thus far.

All characters have been visible in this location earlier on.

Besides all known quirks and bugs in this game, this is by far the most peculiar I've seen yet.