After entering Blackreach, going down the first set of stairs, and traveling down the set path on the right for not long at all, my companion got stuck in place. I've read some other forums and it's been a problem for other people as well. I got a new companion and tested it again and the same thing happened. One solution I read that a person did, is to shout at them until they un-stick, but this didn't work for me. I'm hesitant to bring anyone else in there, which really svcks because there is a lot of loot to potentially have your companion carry. I'm not sure if it happens anywhere else in Blackreach, but it's really too bad, especially if you have a companion that you are attached to or one that you spent money hiring.

Yep, this happened to me. Mjoll was stuck outside the "Silent Ruin" in Blackreach. First time it was fine, went back to do some more looting. She'll follow me into Silent Ruin, and follow me around in there. However, if I leave Silent Ruin, she'll only follow me out the door into Blackreach and refuse to move from the doorway leading into "Silent Ruin".

I tried dropping her as a companion, she neither returned to Sky Temple (Blades HQ) or Riften.

Maybe being a Blades Member has caused a bug?

Dunno.

However, UNRELENTING FORCE worked for me, but only when I shouted it from behind, AWAY from the doorway. Then it was fine.

But, when I shouted it at her, facing both her and the doorway, she didn't follow me.

My companion was Lydia, from the Whiterun castle, but like I said I saved and tested it on another companion and the same thing happened in the same area. I went back and tried shouting unrelenting force at her again, and after repeatedly trying different angles she finally came loose. She started walking off and I assumed she had headed back to the Whiterun castle. A couple hours later I went to use a lift that leads back out to skyrim, and she was just standing there. After I used the lift, she was finally able to return to Whiterun. The same thing has also happened to me that you were describing. My companion has gotten stuck outside of a door I have just exited, but they finally came loose when I got far enough away. Neither of my companions were blades members so you can rule that out. This seems like a really buggy area and should really be patched. It seems that if you don't stick more or less to the given paths, they end up getting stuck/lost to the point that they can't get back to you. Then you end up on the net and joining a forum, spending time trying to figure out what the heck is going on rather than actually playing the game.