I opened a new world in snapshot 19w13a and started playing survival mode with cheats. Everything went fine But then when I started exploring, chunks stopped generating. Whole chunks. I could see a few mobs in the caves underneath but other then that, nothing. I couldn't even walk on the chunks, I would start moving up and down rapidly and have to jump back to stop moving. However, upon re-logging back in after exiting, the chunks were there.