We can't reproduce any of the issues described in this bug report anymore, and it's really hard to hit a moving target (chunks not appearing on the screen can be caused by any number of things going wrong in a looong chain). If you still have this issue, please provide exact reproduction steps if you can; if running singleplayer, please provide a screenshot with the debug screen open and the profiling graphs showing (Alt + F3); if running multiplayer, show exact server arguments + number of active players + at least a rough idea of what those players were doing; a debug dump from the server when the issue occurs will help too (can be obtained by running /debug start followed by /debug stop shortly after). If you can only reproduce it in multiplayer, try to trigger it with as few users as you possibly can, so we can try the same here. Thanks!
– [Mojang] Georgii Gavrichev