Chunk Loading is Unstable (Render Errors)

While I was testing Nether Portal Connections I discovered this problem, some chunks don't render and the only way to load them is to go in the chunks and this can be used to find underground structures (to cheat)
Chunk Loading is also more unstable.

Note: this problem only started / worsened in this Snapshot

Steps to reproduce:
Just go into your world OR create a new one and walk / fly around and load chunks until you see a render error.