The Canary Calls, And I Need Help!

So, in the quest, The Canary Calls, there's a part where you have to solve a minecart puzzle. I did part of the puzzle, then my game lagged and it kicked me out of the server for internet Now, after re-logging doing everything that I could in the puzzle, I figured something was wrong, as I couldn't proceed. So, I ended up looking up a walkthrough, and found that there's supposed to be a crack in the wall right here.

Quite obviously, there's not.
The crack is supposed to open after you complete the puzzle, which I did, and yet there was no crack, and therefor no opening.
So, I tried teleporting to Theasad again, and going to the mines, and again, no crack.

Any help?

 

Ehm, I would help, but I kinda cheated.
See, the wall was already open for me, so I just went through.