When on my Java realm, we teleported a friend over to help us work on a certain build, but when he teleported, blocks of a structure ~10 blocks away were instantly deleted. It also deleted a portion of another build about 50 blocks away. We are certain it was not a mob or a grief. The blocks simply vanished in front of us. Attached below is a screenshot of the affected building, versus an identical structure that is part of the same complex. So far this has been a one-time occurrence, but if it becomes more frequent, could be catastrophic.