Whenever I go to the Nether and come back to the Overworld, some chunks around me fail to load. I can enter the chunks, step on the invisible blocks, break them and get the block I am supposed to be stepping on and everything works fine, but it appears completely unloaded and invisible.
The unloaded chunks also affect my friends when playing online as them too cannot have these chunks loaded when I am hosting the world and enter / leave the nether.
I believe that mobs entering the area also become invisible but I need to test this one more time to confirm it.
The chunk loading problem gets resolved when I exit and get back into the world.