A friend of mine asked me to come help her create a storage room and sort her items into it.  When I got to where she was working, I could see her gamertag but not how she got there.  In the linked video, you'll see that from my perspective, she walked through a cobblestone and gravel wall.

I've included some screenshots that each of us took to show our perspectives of what was going on.  We both logged out of the realm and waited a few minutes before logging back on, and then the problem appeared resolved.  After getting most of the work done, we logged off.  Later when she returned, all the progress in that chunk was gone.  The chunk next to it where the previous chests were that we moved/sorted were gone as they were when we left.  Two of the sorted chests that were in that chunk, as well as some of the floor/wall pattern, are still there.  Items that were in my inventory from the chests that we were sorting are still in my inventory.

Video links:  

Part 1:  https://youtu.be/3iiH-9xELbI

Part 2: https://youtu.be/5MByOpt05O8

Is it possible this chunk is corrupted somehow?  Could this have anything to do with us using different clients?