I was around 4000 blocks away and used a gem to see through a beholder to check in on an amber monolith I had placed near my base. The world didn't load around the beholder so I just saw space. When I pressed shift to stop, I was at Y -1000 or so and died. After teleporting from spawn back to where I was before, some chunks didn't load.
This was working fine this morning, even at long distances. I have no idea what I was doing differently since the last time I opened the game. My other occult gem and beholder were working fine, though there was no amber monolith beside it.