Very slow world loading for particular worlds.

There are a few issues that go along with this. I had tweeted Dinnerbone about this a few days ago, but I don't believe he saw the tweet. The main issue: Worlds sometimes wont finish loading the chunk textures, it seems the chunks are loaded (considering I can walk in them) but the textures wont load until I place down a block. Either that or I have to wait a long amount of time for it to load. In addition to that, it also struggles to load some worlds when you initally open them up. Sometimes It will take a few minutes of the "Loading World" screen in order for the world to finally start showing up, and when it does- I get the previous issue.
The world I've been using is Greenfield. The link to this world download is here: http://www.mediafire.com/file/4yk6702zmzpvvlk/Greenfield_v0.5.1.zip

PS: this issue does not seem to be related to the render distance, I've had it set to anywhere between 12 and 40. I get this issue no matter what.