When changing any setting in the video settings menu that causes the chunks to reload, the chunks don't actually start loading again until you move the mouse. Note that the smallest mouse movement is enough to make the chunks load.

Steps to reproduce:
1. Go to your video settings
2. Change any option that causes chunks to reload (for example smooth lighting)
3. Exit the video settings menu
3. Hold your mouse still and see the chunks won't start loading

IMPORTANT: Changing the render distance does NOT reload the chunks!