Why can't we get the second tome on The Dungeons?

My friend and I were trying to get the achievement for getting all the tomes in the game. We were using this video guide to get the tomes:

Now it appears that this once was glitched as there was a pit that you would fall down as shown in the video. But it has been fixed (according to the video), and here is what it looks like now from my perspective:

You can see that the ground is now solid there, but for some reason an invisible wall is in the way and we cannot get the tome. You can see that in the video they were able to walk right across (another video pops up right as they do so, but looking at the border of the video shows they do make it across and aren't held up by an invisible wall). Surprisingly, we still unlocked the achievement for getting all the tomes after the mission was completed (this was our last mission and we had the other tome with us already). Is there a reason the invisible wall is there? This is on Xbox One also.