One of the companions stopped entering the interior. "Sofia" (The Elder Scrolls 5: Skyrim)

Caught bug after the battle with Ancano, maybe a little earlier. Here's the bottom line:

There are several companions, one of which simply stopped entering the interior.

Using the player.moveto ID command showed that the companion is simply frozen (hanging in the air above the interior).

What could be the reason?

Ps. I know about the method of downloading an earlier save. It was just a matter of time, and it's not a fact that the bug won't happen again after that mission.